MadModder
Gallery, Projects and General => How do I?? => Topic started by: snub on December 10, 2014, 02:09:52 PM
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I'm attempting to add a 12 Volt motor to drive the X axis on my milling machine. The problem is that the motors direction is changed by reversing the power wires. Clockwise direction is power to red wire, ground to black wire. Counter clockwise is power to black wire, ground to red wire.
Here are the parts I intend to use.
One 12 Volt power supply.
Two SPST joysticks. One is momentary for fast table return (not controlled by the PWM). The other will be controlled by the PWM for slow feeding.
One 12 Volt Pulse Width Modulator (PWM) for controlling the speed.
Two DPDT relays ( I have more if needed).
I think I have it figured out without the PWM, but when I factor that in it gets confusing. I tried finding some DPDT joysticks but had no luck.
Here is a pic of the parts.
(http://i53.photobucket.com/albums/g62/mithslew/Machine%20Shop/DSC04036.jpg) (http://s53.photobucket.com/user/mithslew/media/Machine%20Shop/DSC04036.jpg.html)
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You need to implement a 'double pole double throw centre off' function to have FWD-STOP-REV
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That is what I was hoping to accomplish with DPDT relays.
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think iv come up with a wiring diagram that might work for you. ( someone please check as im rather sleep deprived)
have had to assume a few things though, namely :
- the pwm modual requires a + and -ve and outputs a seperate pwm +ve
- the pwm modual dosn't mind having 24v applied to its output
- the joysticks have a neutral point in the middle where none of the contacts are closed
if no's 1 or 2 are wrong we should be able to make minor changes and still be good, if no 3 is wrong we will have to come up with something else.
whoops, that will go bang :zap:
should work as follows:
S joystick moved left, power is applied to PWM modual and R1, pwm signal applied to motor, motor moves left
S joystick moves right, power is applied to PWM modual and R2, pwm signal applied to motor, motor moves right
F joystick moves left, 24v is applied to motor, motor moves fast left
F joystick moves right, 24v is applied to motor, motor moves fast right
iv added interlocks to stop both R1 + R2 ( left and right) being energised at the same time
also if the motor is moving under pwm control and the fast joystick is moved in any direction, it will override the slow speed and move at full speed.
hopefully thats all correct and what you were after, if not it should be a basis to work from.
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- the pwm modual requires a + and -ve and outputs a seperate pwm +ve
- the pwm modual dosn't mind having 24v applied to its output
- the joysticks have a neutral point in the middle where none of the contacts are closed
if no's 1 or 2 are wrong we should be able to make minor changes and still be good, if no 3 is wrong we will have to come up with something else.
I'm totally unsure as to what you are talking about regarding the wiring of the PWM. Picture of the wiring below.
And, yes, the joysticks have a neutral position with no contacts closed. Thanks for your help!
(http://i53.photobucket.com/albums/g62/mithslew/Machine%20Shop/PWMWiring.jpg) (http://s53.photobucket.com/user/mithslew/media/Machine%20Shop/PWMWiring.jpg.html)
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sorry not the best description on my part.
is there any other info with the pwm board? need to know whether the output (motor) -ve is common to the input -ve , hopefully it is or what i drew up last night is wrong
if theres not further info it should be easy to inspect and/or test to find out.
also the way iv drawn things will put 12v onto the motor output + terminal, i dont think this will cause a problem, but the board may not like it. so need to check befor we go much further.
in fact, scrap that diagram, just realised it wrong and will go bang, sorry will have another think and try again
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also just thinking about a few ideas, and would you be happy having to use one stick to get things moving in a direction, then the other to override the speed?
so you'd select left with the latched stick and the motor would move left at the set speed, if the momentary stick was then moved in either direction the motor would continue to move left but at a faster pace, as soon as the momentary stick was let go the motor would slow back down to the set speed.
bit hard to describe but should work as follows:
latched joystick left, momentary joy stick in neutral, :- motor moves left slowly
latched joystick left, momentary joy stick in moved in either direction, :- motor moves left fast
latched joystick in neutral, momentary joy stick moved in either direction, :- nothing happens
it might make the wiring a bit easier but youd not be able to just use the one stick for rapid traverse. i think its how the milwaukee i used to use at work was set up.
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If you add a switch for ON/Off, this is what I come up with using your parts:
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/RC/TableDriveDraft1.png)
Please check before using.
Also please fuse the power supply positive before the switch.
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Thanks for your help guys. Problem is I'm somewhat baffled when it comes to schematic diagrams. I'll see if I can figure it out in the morning.
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Hi
simpler way is to add wires to the pot on the controller middle terminal and the High speed side of the pot and a closed switch will give full speed.
Use the relays one for forward and one for reverse controlled with one joystick and the other one to short the wire on the pot.
Remember to allow the motor to STOP with the mains power switch off before reversing
Eric
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That would mean ignoring existing wiring terminals and soldering wires to the pot.
Not sure how that's simpler....
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Snub, here's an explanation of the schematic symbols. A schematic is just a wiring diagram -- the lines are wires.
A relay is just a switch that is pulled in by an electro-magnet (or coil). If you power that coil it attracts the armature and closes the switch.
Most relays have a normally closed switch and a normally open one. (So they are double throw ---- DT)
Double pole relays (DP) have two switches, both of which have normally open and normally closed contacts (or poles).
Hope this helps you figure out the schematic! :dremel:
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/Shop/SchematicSymbols.png)
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Thanks very much vtsteam. I said that the joysticks were SPST, when in fact it they each have 4 SPST switches independent of each other. I will only be using 2 of the switches on each joystick. In your schematic it appears that only one switch per joystick is being used. I will grab a picture if that will help.
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Yes, Snub, I took you at your word on SPST, so only one switch is shown for each joystick.
I don't think I'd change anything for 4PST. You could parallel all 4 if you want -- or just use one of them.
Now if they'd been 4PDT, we could have gotten rid of relays (or even 2PDT).
And of course a "center off" Joystick would have been nice, as Andrew said -- and would have eliminated the extra ON/OFF switch needed.
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And if you decide to build it according to the schematic, here's a suggested build sequence:
1.) connect the Joysticks and relays, power supply, and ON/OFF switch as shown, but don't connect the motor or PWM speed controller yet.
2.) check to see that moving either joystick causes its respective relay to "click" in.
3.) connect the motor, but don't add the PWM yet.
4.) check to see that moving the speed joystick will start the motor at full revs, while letting go turns it off
5.) check to see that the direction joystick changes the direction of the motor.
6.) check the wires that will connect to the PWM input have the correct polarity by measuring across them with a meter.
7.) with power disconnected, connect the PWM to the circuit.
8.) set the potentiometer to mid position and connect power to test the whole circuit.
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Potential problems to look out for (I assumed all parts had suitable specs for your purpose......but here are the possible problems if they aren't) :
Switch contacts not rated for relay current, or back EMF.
Relay contacts not rated for inductive load of motor
Relay arc suppression needed
PWM doesn't like output disconnected/connected
The first three would mean shortened component life.
The last might mean PWM dies.
The PWM output problem -- if it happens -- might be solved with velocette's potentiometer shorting method. Though changing direction will still momentarily disconnect the output, so, maybe not.
.....Shouldn't happen -- a brushed DC motor is constantly making and breaking current....... so if this PWM is designed for motors, it should handle a switched output.
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Following on from VT's testing procedure,
I'd suggest using an auto bulb(lamp?) in place of the motor and connect a fuse in series with the +ve supply lead ( use a 5watt bulb and a 1A fuse power the whole thing with a 12v battery before you use a big power supply...might stop any magic smoke coming out. )
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from the looks of those joysticks and the info given i thought they had 4 N/O contacts, 2 of which are closed going left, and two going right, with a neutral in the middle where all contacts are open?
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John, good idea!
Bertie, Well then they'd be 2P3T center off switches. Which would have made things a whole lot easier......
The 64 thousand dollar question, Snub..........
How many positions does the joystick have, 2, or 3?
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they would indeed!
pics seem to be standard N/O contacts in pairs on a standard switch block.
[/quote]
And, yes, the joysticks have a neutral position with no contacts closed. Thanks for your help!
[/quote]
unless im mistaken ?
makes the direction control with one joystick easy but i think the relays are still needed if you want independant controll on the second joystick, iv got something drawn up but it needs electronic interlocks
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These joysticks seem to be causing some confusion ( my fault ). They are 4 way joysticks with 4 separate SPST switches. They go left, right, up and down with center off. I am only using the left and right. All are normally open contacts. Too make it simpler when I was trying to come up with my own wiring diagram I left out the joysticks and drew 4 separate SPST switches. Unfortunately my scanner isn't working because I'd like to post it. I am trying now to fix it.
For now I will leave you with this:
One SPST switch for left (with PWM)
One SPST switch for right (with PWM)
One SPST switch for left (full power)
One SPST switch for right (full power)
Thanks guys!
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Oh, 4 way center off SPST joysticks! :doh:
Okay, well we can use the center off feature to eliminate the ON/Off switch I showed in my schematic.
The direction relay will stay.
The speed relay can be eliminated, IF both joysticks are non-centering. Can you change the joystick that centers to a non-centering joystick, mechanically? That's often possible -- part of the design.
If not, the circuit I showed will function fine since it was designed for only one SPST joysticks. And at the least, you have that.
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After noodling around, my head hurts now, and I'm taking a break from this -- I want to work on my shop!
But if interested the circuit I showed will work fine as-is. The joysticks will act like two position sticks, even though you have 3 positions -- two positions will be the same and the third will be the other choice. The ON/Off switch will what it was meant to do.
Maybe later tonight I'll think about it again, but for now there's one working circuit out there, at least.
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After noodling around, my head hurts now, and I'm taking a break from this -- .
Yeah....can't say I blame you....
I'd say there's an easier way to do this....but I don't want to confuse the OP any more....
Suffice to say, In my experience,pwm drivers have an open Source out...simplest way for max speed would be to just short the mosfet...but that needs a high current relay contact.....but then you could just pull the Gate high........hmmmm....
Watch for smoke.... :lol: :lol:
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Well got a little done on the shop, and now it's dark.
A big enough diode to handle the amps would even do it:
The speed joystick SPST switches wipers would be hooked together (making them a SPDT). That side would be connected to power +.
One switch's output goes to the speed relay coil. And also, through the diode, to everything else needing power.
The other switch terminal output goes to everything BUT the speed relay. Diode prevents back feeding and energizing the speed relay.
Position 1 -- energize speed relay and rest of circuit
Mid position -- no power to anything.
Position 2 -- speed relay not energized, power present to rest of cicuit
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Ugh.... just remembering that one of these joysticks is "momentary" (from first post) -- does that mean it's self centering? Probably.
In fact I'll bet they're both self centering --- yes? Typical 4 way switch joysticks, right?
Okay ditch the reversing joystick and the reversing relay and just buy a simple DPDT switch for direction. There's no point in a 4-way self centering joystick and relay for this!
And for the other, just rig up a momentary push button for fast traverse! You can do it with velocette's pot shorting method.
Add a RUN/STOP switch and you're done.
Then things truly are simple!
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Thanks for all your effort, vtsteam. It is much appreciated. When I was a youth I could comprehend all of this but my 60 year old brain is not what it used to be. Those joysticks are a joy to use and that's why I wanted them. I was searching Ebay today and think I may have found some DPDT joysticks. Plan C is I will simply use some DPDT switches and add some long handles. I just hate buying new stuff when I already have a bunch of parts that need to be used somewhere.
Again, thanks to all for your help.
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No problem Snub, puzzles are fun, but sometimes you reach a dead end -- or at least I did.
The real problem was that spring loaded centering joysticks had no way to maintain a direction.
If center was forward, how would you put it in reverse without holding the joystick over? You need a detent at both ends of the throw, and no middle position -- like how a normal 2 position toggle switch works.
Fast traverse/slow cut would work okay with one of your joysticks, if you made the center position the slow cut speed, and one end or the other the fast traverse. Since that only needs to be momentary
But since you really have a 4 position stick you would have to waste 3 of those outer positions -- as either redundant, or having no effect. It's certainly do-able, but not what I think you wanted.
Ideally you would have a 3 position stick, not spring centered, that gave fast, off, and slow as the three positions. But it would have to stay in each of those positions, except fast, which could be momentary.
So the real difficulty was that the sticks were self centering. We can't make up for that with circuit changes. It's a mechanical problem.
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These joysticks seem to be causing some confusion ( my fault ). They are 4 way joysticks with 4 separate SPST switches. They go left, right, up and down with center off. I am only using the left and right. All are normally open contacts......
IF the movement is constrained so only one switch can be operated at a time (i.e. only N, S, E, or W) by an irremovable " + " shaped gate then ignore this.
However, IF the movement is unconstrained and you can move it to any direction in a circle (in particular NE, SE, SW, NW) then here's a suggestion for the 'user interface' using just the one joystick:
UP (high) and right - High speed to the right
DOWN (low) and right - Low speed to the right
....and similar to the left
Dave
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Yes Dave, but with self centering joysticks you'd have to hang on to them throughout the cut. (also, I think this is only a single axis drive. The functions needed are ON/OFF, FWD/REV. and MILL/TRAVERSE.)
The only true "joystick" operation should be fast traverse. Let go of a stick and it stops. Everything else should be able to hold in position. It's a mechanical problem, not a wiring problem.
Imagine if a car transmission stick returned to neutral as soon as you let go of it.
The controls need to stay in position. That's the function of a bat switch, not a joystick.
The other function of either of these is to indicate intuitively what is going on. A forward handle should indicate forward travel, for instance. Or high speed, etc. Thus "blip and latch" electronic controls (like the volume button for a TV remote control) have poor user feedback when used for a machine drive. Handle position is extremely useful as an indicator, as well as a means for changing an operation.
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i think im really confused about those joysticks now.
so they both have 4 N/O contacts one for each direction, up down left and right?
one of the joysticks is momentary and returns to the center
and the other one? my understanding was it wasnt momentary, so therfore must latch in whatever position its moved to e.g left
do you have any info from the supplier? i think they may be modable to 2P3T
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The joysticks only move in a "+" shaped gate. 4 separate SPST switches with center off. Much like the controller for an old video game like Pacman. You can move your "man" up, down left or right. But you can't move up and right (for example) at the same time.
I chose the "latching" one for slow speed milling (in both directions) so I could stand back and watch the machine work without having to hold the switch on. I chose the momentary switch for fast travel in both directions since the table moves quite quickly.
I chose the 4 way sticks for 2 reasons. First, I may add a motor to the "Y" axis so I could use the same sticks to control that. Second, they were dirt cheap. $16.00 for the pair delivered from China. They were manufactured by Schneider Electric, but are obsolete, so not much info available.
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Hi
I fully understand this ""Plan C is I will simply use some DPDT switches and add some long handles.
I just hate buying new stuff when I already have a bunch of parts that need to be used somewhere"".
They are certainly a pleasure to use hence the name "Joystick".
Have Added A sketch of the system I use on a similar controller plus photos of latch to prevent "Instant Reverse"
Eric
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So, snub, one of your sticks latches at either end of the travel? It will stay in the position you put it in? Because if that's true, then it is possible to work it out.
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Yes, the joystick for the slow speed machining maintains its position until you manually return it to neutral, just like a normal switch. Thanks for your help vtsteam, but I think for now I am just going to throw some DPDT switches in there and be done with it. If I decide to add a motor to the Y axis, I may then persue this.
I did a project similar to this years ago and now I recall that I had problems with the relay coils not de-energising fast enough when I was reversing the motor direction. If I flipped the switch too fast, I would blow the fuse. I believe it was the fault of the PWM. It had an LED light on it to show it had power but when you turned it off the light would still glow for several seconds, then slowly dim to nothing.
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Darn, Snub, I finally had an idea that I think would work very easily and straightforward. I could draw it up quickly with those sticks.
Instead of one stick for direction, and one stick for speed, we could make one stick for high speed, and one for low. Direction could be set by either stick -- forward for forward, back for reverse. Both sticks in neutral would be motor off. This would require only your two relays. The slow stick would detent in either forward or reverse.
If you wanted to add another axis, all functions would be the same for that axis as well, so it would work perfectly for a 4 direction joystick. One stick would be fast traverse for both axes, and the other would be slow for cutting for both axes. Very simple to set up and the circuit diagram would be symmetrical.
Your problem in the past was due to the motors acting as generators before they stopped when you reversed direction -- that increased the current momentarily, blowing the fuse. You might get by with a slo-blo type fuse if the current spike isn't too great. Also with a center off position, you might get a little more time for a slowdown before reversing.
The reason the LED glowed after it was turned off was unrelated -- there was just probably a capacitor in the circuit wth the LED, and it needed to discharge completely before the LED stopped glowing.
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Instead of one stick for direction, and one stick for speed, we could make one stick for high speed, and one for low. Direction could be set by either stick -- forward for forward, back for reverse. Both sticks in neutral would be motor off. This would require only your two relays. The slow stick would detent in either forward or reverse.
That is exactly how I had envisioned it working. I know now that I hadn't explained it properly in my first post. Either that or we need a USA/ Canada translator. Living in Vermont you are not far from Canada but I know your immediate neighbours to the north don't speak the same language.
The problem I am having is converting your schematics in to actual wiring hookups. All is good except for the relays. My scanner is still on the fritz so I can't show you what I came up with, but here is a picture of how I drew up the wiring diagram when I motorized my lathe. Works perfect.
.
'
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well iv had another quick go at a possible solution and have come up with the following:
(http://i655.photobucket.com/albums/uu280/b-bassett/Mobile%20Uploads/WP_20141214_002_zps45d397c6.jpg) (http://s655.photobucket.com/user/b-bassett/media/Mobile%20Uploads/WP_20141214_002_zps45d397c6.jpg.html)
the latching joystick sets thing in motion at slow speed, and the momentary will bypass the pwm for full speed.
if the momentary joystick is used on its own, nothing will happen.
not quite what you were after but it might do you?
two things to note though, iv common'd up the pwm -ve with the supply -ve, and in fast mode 12v is supplied to the motor and the + output of the pwm modual. i dont think either of these will be a problem, but without the part in my hand i cant be sure
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Bertie, hard to read as drawn, but looks like in the state you show your circuit you have PWM + going to both sides of the motor. Haven't checked anything else.....
snub, sorry about my own mistakes in reading your first post. I'll try my hand at a drawing one more time and post something (I hope) tonight. I'll try to make it more like your drawing and less like a schematic, if I can.
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snub, okay I worked out a circuit. It is for only one of the joysticks, and one of the relays just to make it easier to understand.
The other one would be identical except it would also include the PWM in the circuit. The one I'm showing here would be the fast speed Joystick and relay. I'm going to show it first as a schematic, and later try to do a block wiring diagram like you showed.
But I'm hoping that you will be able to "get" what's happening here first, since if you have the concept, it will be easy for you to draw out your own diagram.
First, here is the schematic (I'll explain it next post):
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/Shop/NewTableDriveSingleSchematic.png)
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Okay, the explanation:
Your relay should have 8 connection locations on it.
2 for the coil (from your picture, first post, it looks like they are the bottom 2 larger lugs)
6 for the DPDT switch that the coil operates.
That DPDT switch is just like any other normal DPDT switch. It seems like you know how to wire a DPDT switch -- this is no different.
As you probably know, a DPDT switch is basically two switches in the same case that are mechanically connected together, so they close at the same time. And those two switches have a center movable contact that closes with fixed contacts at ether end of the switch. So you have two connected positions for the switch.
Using the DPDT switch analogy, a relay has a spring in it holding the switch closed to one side. When power is applied to the relay's coil it moves the switch to the other side. That is the whole operation of a relay.
The center contacts on the relay's switch are called the "armature", and the switch's end contact is either referred to as "Normally Open" or "Normally Closed", depending on which end it is located at.
When no current is flowing through the coil, our switch is held by the spring to one side, and the contact on that side is the "Normally Closed" contact. The contact on the other side is not connected to anything, and so is the "Normally Open" contact. That's all there is to that.
Your relay should have the connection lugs labeled, and/or a small schematic diagram indicating which contacts are which. If you can include a picture of that it will be easier to draw you a wiring diagram, like the one you showed.
Okay, so that's relays. Next, the joystick.....
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The joystick you have is a 4 way joystick with 4 SPST switches, one for each direction, and a center position where no switch is closed.
I don't know whether all 4 switches are connected together on one contact of each switch (in other words they have a common connection) or whether they are completely independent,
We want two of the switches opposite each other to be connected together on one of their contacts. So if the joystick is already common connected, fine. If not, you can do that manually with a short wire.
That common point will also be connected to the + side of your power supply.
Therefore, when you move the stick to either extreme, one or the other switched contacts will get + voltage on it.
So much for the joystick. Next......
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Now our relay coil can only be ON or OFF, but we have a joystick with 3 positions on it -- Left, center, and right.
This means two positions of the joystick (center and one side) will have to do the same thing, as far as the relay goes.
I'm choosing to de-energize the relay for 2 positions of the joystick, and energize it for one. So how do we get 3 different results with the mill table out of that?
To solve this problem we are going to let one joystick switch make a dual connection, and the other switch make a single connection, while the center position will make no connection -- three different circuit results, which can yield three different movement options for the mill table.
The first switch will pull in the relay, AND supply current to one relay contact. In this case a Normally Open (NO) one. Since the relay will be energized, this contact will be closed, and if it is connected to the motor, it will run.
The second switch will NOT be connected to the relay coil, so cannot pull in the relay. Instead it will be connected to a Normally Closed (NC) contact and since the relay isn't energized, that contact will be closed, and will be able to pass current to the motor. In this case it will be connected to the opposite contact on the motor than the first switch was, and so it will run the motor backwards.
The middle joystick position, will not connect the + side of the power line to anything. Not the relay coil, or any contacts. Therefore, the motor cannot run.
The rest of the circuit is there to connect the minus power supply to the relay contacts, in such a way that it gets connected to the correct side of the motor to complete the circuit, depending on which joystick switch is active.
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Here is a picture of the first schematic (without labels to make it easier to see) and the same circuit with the PWM added -- this would be the second joystick, the one with the detents.
Obviously they would share a power supply when you build it, but I've kept that apart to make it easier to read here. You would probably also add a fuse, pilot light, and on/off switch for the power supply -- but again, I left them out for clarity sake.
(ignore the pin numbers on the PWM in the drawing -- they were auto-numbered and may not match your PWM speed controller)
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/Shop/NewTableDriveSinglesm.png)
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vtsteam, I really appreciate all this but I'm still slightly stumped. On your schematic/diagram (post #39) it appears to me that the relay has 10 connections. My relays function exactly as you described in post #40. I have to go as there is smoke pouring out of my ears from overloaded brain.
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Snub, sorry -- I think I see your problem -- the circles (hollow dots) are contacts inside the relay. Black dots are the lugs outside of the relay where you make your connections to it. The arrow represents the movable part of the switch.
So there are:
2 lugs on the relay for the coil
and 6 lugs on the relay -- for the two switches.
each switch has a center movable part, and two contacts, one normally closed, and one normally open.
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Here's a picture of a relay:
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/Shop/DPDTRelay.jpg)
It's a DPDT relay without a case. You can see the two different switches. I've labeled the parts. The upper contacts are the NC ones because the spring is holding the ramature's contacts up against them. The lower contacts are the NO contacts because the armature contact is not touching them.
If the coil is energized, the armature pulls down and breaks the connection with the upper pair of contacts, and makes a connection with the lower pair.
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Relay contacts without and with coil energized. The middle contact is the armature:
(http://3.bp.blogspot.com/-vbaqxKdXGO0/Uu3jBSFtwiI/AAAAAAAAALE/Co8qqnGvdMI/s1600/Form-C+contact+in+both+positions.jpg)
Schematic version:
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/Shop/Contacts.png)
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Here's a simple relay (SPDT), and a DPDT relay.
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/Shop/Relays.png)
Notice there are 8 connections to a DPDT relay.
2 to the coil
NC, NO, and armature to one switch
and
NC, NO, and armature to the second switch.
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Believe it or not, I am grasping everything..........except the connections to the relays. Once we get through this we will be good to go and you can get back to your own projects. Unless you are up to your waist in snow. Here is a picture of the relays I am using and their terminal connections. Got to love those clear plastic cases, you can see the guts inside. No guessing as to the proper hookup.
Update:
Don't bother clicking on the picture. The diagram is wrong.
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Snub,
I suspect that the connection diagram you posted for your relay is wrong!
From the Picker website (and in common with most other similar relays):
(http://listerengine.com/coppermine/albums/userpics/10017/dpdtrelay2_zpsf97eb404.jpg)
So, in the diagram you posted the Armature and Normally Open Contact connections are swapped over.
You need to connect the relay as follows:
(http://listerengine.com/coppermine/albums/userpics/10017/dpdtrelay_zps68d7828b.jpg)
I hope this helps.
Cheers.
Phil.
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I have been watching this thread and decided to throw in my 2 cents. Steve's' circuit is spot on and the explanation is easy to follow. There are just a few comments I would like to make.
1. Most relay contacts are labeled NC, NO and COM (common ). In this case the motor armature is connected to the common terminals but the relay coil is also called an armature in some designs.
2. In the first schematic the joy stick is shown in the on position while the relay is shown de-energized which can be a bit confusing.
3. A suggestion: Using a DPDT switch the speed controller can be switched in or out of the circuit which would eliminate the need for a second joy stick.
4. It may be wise to add limit switches on both ends of the travel to protect the drive.
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.....3. A suggestion: Using a DPDT switch the speed controller can be switched in or out of the circuit which would eliminate the need for a second joy stick......
except that then raises the issue of which joystick to use - latching or non-latching? - unless Sub is going to make his own gates.
and ....
The circuits above have the motor power routed through the joystick contacts. I can't recall the specs for the switches being posted but I suspect they're more likely to to be signal-rated than significant-current-carrying? - in which case you may need an extra relay (and maybe a couple of steering diodes).
And .... re my earlier suggestion (#28) of a user interface, if you have the option of making your own gates, then there's a simple way I've just thought of to use just the one joystick - if your gate is "+" then mount it 45 degrees round so you get an "x" gate :doh: so you could still have up/right (unlatched) = high speed right, down/right (unlatched) = low speed right, etc.
Dave
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ahh yes id put the N/O and N/c round the wrong way.. :palm:
looks like you've got it pretty much sorted now though :)
one thing im not sure will work with the above diagrams though, is the use of the pwm to power the relay coil. im not sure the relay will like that?
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Snub,
I suspect that the connection diagram you posted for your relay is wrong!
From the Picker website (and in common with most other similar relays):
So, in the diagram you posted the Armature and Normally Open Contact connections are swapped over.
You need to connect the relay as follows:
Phil.
You are absolutely correct. I screwed up. Again. I think I must have used up all my brain cells.
My lack of proper knowledge of the nomenclature caused me to think that terminals 3 and 4 were the armature.
Terminals 1 and 5 and terminals 2 and 6 have continuity with no power to the coil.
Terminals 3 and 5 and terminals 4 and 6 have continuity when power is applied to the coil.
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Snub, check and post the switch ratings for the joystick -- should be located on the switches themselves, or online from the company you bought them from.
The PWM output driving the relay could be an issue -- maybe put a cap across the relay to keep it high enough in voltage and smooth. And add a diode in series to keep it from backfeeding anybody else......
Guys, I'm out of further ideas unless we add relays, or logic components, or different joysticks which, kinda gets away from the easy theme using the available components.
Anyway -- best I could do! Time for me to let better electronic minds have at it! :bow: :beer:
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Info from the switches:
Ui: 600V
Uimp: 6kV
240 V 3A
lth: 10A
My motors actually draw less than 2 amps so I should be good there.
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i think those switches should be ok, DC currents are harsher on switches then AC but shouldnt be a huge problem in this situation.
i suspect the switch contacts could have extra's piggy backed on the back of them , perhaps the up and down contacts could be re-positioned?
i dont think your far off with the current diagrams, just a bit of tweaking for that pesky pwm
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I'm addicted to this problem. I think I'm burned out. Then I look at this thread again and.........
Okay shotgun approach to the PWM relay issue:
Add another power supply.
Could be just a little spare DC wall wart with enough juice to kick in the relay.
Here's the same schematic as before with the relay negative lead detached from PWM , and connected to New Power Supply.
The positive side of the supply hooks to the PWM + side.
(http://i786.photobucket.com/albums/yy150/vtsr/vtsr/Shop/NewTableDriveSingle2pwr.png)
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vtsteam, I appreciate all your help, but I think you have gone far and beyond what I would expect a total stranger to do to help me out. I am starting to feel guilty. But if you are so inclined, please carry on.
That power supply that I showed in the first picture was dirt cheap. $16.00 delivered from China. It even has a "trimmer"? that will set the voltage from 11.5 to 14.5 volts. Vendor calls it a" voltage output fine adjustment."
Here is a link to it in case anyone needs one. Will work on 110V or 220V.
http://www.ebay.com/itm/390838271618?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
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Those are sold widely as 'LED supplies' on eBay UK. I used that exact model when I fitted that strip led light in my Traub CNC lathe. Seem reasonably well made and good value for money.
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Ok might have got it sorted now. Just one extra part needed,
Rather then an extra power supply, just put the supply to the pwm modual in parallel with the relay coil, and its outputs direct to relay contacts.
That would give you slow speed in one direction, for the other simply put a diode or extra switch between the joysticks switches so that only the pwm gets power, not the relay.
I'm not able to draw it up at the moment as on phone, but can sketch it up later if required.
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That power supply that I showed in the first picture was dirt cheap. $16.00 delivered from China. It even has a "trimmer"? that will set the voltage from 11.5 to 14.5 volts. Vendor calls it a" voltage output fine adjustment."
Snub, don't feel guilty, I'm just kidding about working on this particular circuit problem! :)
Also nothing wrong with your power supply -- I just meant add a very small second power supply -- like a wall wart -- which most people have kicking around from unused equipment.
The second power supply will provide the relay coil with a stable voltage when needed, rather than depending on the output of the PWM to do it, which is a variable voltage.
Since the relay coil doesn't need much power, a small wall wart type power supply of the right voltage and current rating should be easily able to handle the needs of the relay coil. This small supply could even be hard wired and built into whatever case you will be putting your main power supply in (if any).
I actually have a commercial CNC controller that had a big power supply (like yours) for the stepper motors, and a small wall wart to power a circuit board, built inside the aluminum enclosure). I only saw the wall wart when I opened the case of the controller to set some DIP switches for different steppers.
So it really doesn't matter what power supply you have chosen to power the motor, this second small DC supply would only be used to close the relay.
The output of the PWM isn't the best thing to use to operate the relay, since, well, if you turned the control down to zero, the relay couldn't pull in at all. And it may not be able to pull in at speeds higher than that and into your useful range of table travel speeds. So the simple thing to do is not use the PWM output to power the relay.
I suggested a wall wart rather than a diode (and you probably don't know what that is), because you're more likely to have a spare power supply on hand,, and it would be a very simple and straightforward circuit change for you. And easily understandable.
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This Works
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Hey thanks for the linky!
Thats a great price for a 150 watt 12 V X 12.5 A psu
In europe I paid about €80 for a 12v x 8A psu to run a beer cooler!
Should help the induction heater project nicely (when I stop blowing mosfets)
Work in Progress sums it up
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had a lil bit of time to play around with a modified circuit and this is the best i can come up with
(http://i655.photobucket.com/albums/uu280/b-bassett/motorpwm_zps3253151a.jpg) (http://s655.photobucket.com/user/b-bassett/media/motorpwm_zps3253151a.jpg.html)
2 options for the pwm circuit, either an added diode, or an extra switch added on the back of the joystick.
personally id try to modify the joy stick for an extra contact.
vtsteam: i dont think your extra power supply will work as drawn as its putting a permenant supply onto the pwm output so you wouldnt get any slow speed
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Bertie, I like your diode version. And better than the switch version, since the problem was to do this with joysticks, not switches.
I'm not 100% clear why my circuit would do as you say, but one problem with the drawing (pointed out back a ways by 75 plus) is that I showed the joystick contact as closed and the relay is shown in its un-energized position. This might be why I'm missing what you're saying, because I'm back at the head-hurting stage trying to imagine what happens with the relay energized, or the joystick in the opposite contact (to make the drawn schematic consistent).
Likewise, I'm having a hard time imagining that effect on yours since you used my same schematic. Both need re-drawing. But in principle, I like your diode method.
The easiest change to the drawings to make them consistent, would be to draw the joystick common (arrow) going to the lowest contact rather than the upper one.
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velocette, yours works but doesn't fit the requirements for a high speed joystick and a low speed joystick, each with a center off position.
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The motor is always started on Low speed Then engage the second momentary switch On the joystick to Give high speed by shorting the speed Pot.
A lot less load on start up than reversing at full speed. Works For Me
Eric
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sorry for the confusion, when i mention switches, i was refering to the contacts on the joystick itself. in this case there are 4 seperate N/O contact blocks. easiest to think of them as 4 seperate switches.
vtsteam: your drawing with the joystick closed but relay de-energised is a bit confusing, but dosnt really effect much. The modifications i drew up from your drawings, accounted for this and should work as drawn. ( the origional fast speed would need minor wiring changes, but nothing major)
as iv drawn things it dosnt really matter what state the relay is in, your primarily turning the pwm modual on to power the motor, direction is a secondary affair.
the biggest problem with PWM is that its basically just turning the motor on and off very fast, so if you were to feed a relay with it, it would be going on off on off on off which i doubt it would like at all.
adding a constant power supply onto the same rail would just override the PWM as there would no longer be the 'off' section.
overiding the pwm was basically what my origional idea was, get things moving in the direction required at slow speed, then override the pwm to speed things up a bit!
hope that clears things up a bit.
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vtsteam: your drawing with the joystick closed but relay de-energised is a bit confusing, but dosnt really effect much.
Well it's my mistake and it does actually show an impossible state, and is confusing when trying to trace what is happening, so I'm claiming it as a problem -- at least for me! :)
I believe the PWM version of the circuit (not the high speed version, which is fine) that I showed is just plain wrong as a direct result of mis-reading the circuit, based on my mistake in showing the switch closed and the relay opened. I might be able to re-draw it properly, but I need a mental break from it for a bit. I do like your diode version if it proves out.
the biggest problem with PWM is that its basically just turning the motor on and off very fast, so if you were to feed a relay with it, it would be going on off on off on off which i doubt it would like at all.
Nah, I see the reduced effective voltage to the relay if the PWM is turned down as a problem. not the fact that it's pulsed DC. But that's moot. It's obviously better to feed it straight from a full voltage DC power supply in either case.
hope that clears things up a bit.
They were clear already, so no problem. :beer:
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Lets edit my earlier explanation to make it clearer please see the PDF File I Posted on "This Works"
Snub in his original posting shows 2 Joysticks 2 Relays 1 Power Supply 12 volts DC 1 PWM speed control 1 12 volts DC motor
Attempting to use the Existing equipment as indicated for the starting base for this circuit.
The motor is always started on Low speed with the latching Joystick Fwd Off Rev.
A lot less load on start up than reversing a relay engaged at full speed.
Substitute the Push Button with the second Joystick with Momentary Contacts
Then use the contacts On the Second joystick to Give high speed by shorting the speed control Pot to High Speed
The High Speed is maintained as long as the Second Joystick is held Closed.
Eric
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whoops just noticed my diode was in the place :Doh:
heres an ammended drawing, iv also redone the 'confusing' relay situation, should be easier to read.
(http://i655.photobucket.com/albums/uu280/b-bassett/motorpwm_zpse311aee2.jpg) (http://s655.photobucket.com/user/b-bassett/media/motorpwm_zpse311aee2.jpg.html)
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Well, Berte, now all the relay contact designations and pin numbers PhilF clarified are wrong. Look out Snub! :zap:
(I said the joystick wiper needed to be moved to a different position),
Diode in wrong place.............this is getting to be funny! :lol:
I guess we'll muddle our way to something that makes sense.
Kinda like chimps typing up Shakespeare's Hamlet by hitting random keys -- eventually
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Ahh it will all work in sure, iv only put the relay contacts in an energised state. ( although technically thats the wrong way to draw a schematic). Shouldn't go bang.
I think we've moslty got it now, just need that diode or extra switch adding to the joystick.
In regards to that diode, it will need to be capable of handling the motor current ( plus a bit extra) as its feeding the power to the pwm modual. So a spec higher then 12V 3A should do the trick.
Its been far too long since I draw up proper drawings, but the knowlage is on there somewhere.
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Better specify 100 PIV or more while you're at it.
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Well it seams like I'd best wait a few days before wiring it up in case there are any more last minute design changes.(http://i53.photobucket.com/albums/g62/mithslew/funny/1.gif) (http://s53.photobucket.com/user/mithslew/media/funny/1.gif.html)
Seriously tho, I really do appreciate the help. And I bet some of you are enjoying the challenge.
(http://i53.photobucket.com/albums/g62/mithslew/funny/salute.gif) (http://s53.photobucket.com/user/mithslew/media/funny/salute.gif.html)
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I haven't looked closely at Bertie's new circuit, and my last one for the PWM control joystick was wrong.
The fast traverse joystick seems to be right, except the Joystick switch should be shown on one of the lower contacts to be proper. These dwgs, should also have the relay pins properly arranged and labeled once the circuit isn't set to fry. :zap:
I might get back on the PWM circuit suggestions later tonight. :coffee: