Building a Penny Pusher Arcade Game

[Bluechip]

Hi guys, thanks for the interest!!

I just thought pwm would give me control of the speed as I'm not sure exactly what speed will work best. Anyway, taking your advice, 9v seemed about the correct speed. Looked in my box of old supplies and to my luck 9v. 1500mA.  One of those small Chinese made supplies. Anyway, connected it up and it moves at about 1/2 RPM is there really jurky fashion!!
I must be making an obvious mistake :-(

Possibly because it's a switched mode device, never intended to drive a motor.
It may well be going into over-current, shutting down, coming back up, over-current, shutting down etc. etc. ad nauseum.
 
I assume you are aware that Chinese milliamps aren't as big as real ones ??
 
That motor, at switch on, is going to look pretty damn close to a short circuit ... they all do.
 
Dave BC
 
 
 
 
 

[raynerd]

Yep, I did think the answer would be something like that.

Now to try and find a 7-9v supply suitable! :-(

[vtsteam]

How about a 6 volt transformer, a bridge rectifier and a big capacitor paralleled with the output? Good old fashioned tube (valve) filament power supply. 3 parts.

[vtsteam]

Okay, okay, add a fuse and a power cord and a box, etc.


-or-

I did test the original controller you were interested in, made a video of it running, and gave you speeds and current draw as requested.

And as you can hear in the video, no hum. Just gear noise.

[NeoTech]

Those last pesky details..   

[Bluechip]

Wouldn't even use the capacitor, DC PM motors run quite happily on rectified AC.
 
Dave BC

[BillTodd]

Hi guys, thanks for the interest!!

I just thought pwm would give me control of the speed as I'm not sure exactly what speed will work best. Anyway, taking your advice, 9v seemed about the correct speed. Looked in my box of old supplies and to my luck 9v. 1500mA.  One of those small Chinese made supplies. Anyway, connected it up and it moves at about 1/2 RPM is there really jurky fashion!!
I must be making an obvious mistake :-(

How much current does the motor draw?  Mayne be too much for the supply - windscreen motors tend to be quite beefy and not too efficient so may require more power than you expect .

[Edit]

Just measured a two speed wiper motor at  1.2 and 2.2 amps at 9v (unloaded ) it draws about the same at 12v

Power on surge could easily be 10amp!

Somewhere, i have a circuit I designed for a positive feedback (resistance compensated) speed controller ...

[vtsteam]

How much current does the motor draw? 

http://madmodder.net/index.php/topic,8810.msg96161.html#msg96161

This has already been tested, is rated at 10 amps and works:

http://madmodder.net/index.php/topic,8810.msg96103.html#msg96103

As shown here:

http://madmodder.net/index.php/topic,8810.msg96117.html#msg96117

[raynerd]

Used a few ATX supplies for various jobs over the years.


They have a 5v line and 12v - do they have a 7?? If not, maybe this is terrible electronics but wont using the 5 and 12v lines give me a potential difference of 7v ?? 

[awemawson]

Beware: Often, PC power supplies will not start up unless there is a load on (usually) the 5v supply. This supply is used as the one for feedback for voltage regulation, and all the others remain at voltage by ratio.

[Bluechip]

Used a few ATX supplies for various jobs over the years.


They have a 5v line and 12v - do they have a 7?? If not, maybe this is terrible electronics but wont using the 5 and 12v lines give me a potential difference of 7v ?? 

Yes it will, but it won't be 7V emf ...    think about it ...
 
A 12V supply pushing out current through a load to 0V
 
A 5V supply doing the same ... ie  out
 
OK . as awemason rightly says most ATX's wont power up unless the 5V is loaded, often to about 1A. which means a 5R resistor.
 
PSU now comes up OK ...
 
Now connect your motor from +12 to +5 , the motor can now sink it's current through the 5R resistor
 
Except it's start current will be ( modestly ) 3A which will try to drive the 5V O/P up to 15V.
 
Well it won't get there 'cos it's only got 12V to start with.
 
The 5V will not see the funny side of the joke, will sense over/voltage and shut the ATX down.
 
You need to visit the difference between 'PD' and 'EMF'  and 'sourcing' & 'sinking'.
 
The 5V supply can only source 5V, the chances are it can't sink the 12V.
 
Not while it's alive anyway ...
 
You seem to be looking for the most abstruse solution you can devise to a non-problem 
 
AS Bill Todd, VTSteam et al have alluded ..
 
Get a 0-6 0-6 50-ish VA transformer, nail it to a 15A bridge rectifier, switch on, slide off for a pint while you leave it to ekkle.
 
Dave BC
 
 
 
 
 
 
 
 

[vtsteam]

The one secret we haven't mentioned to Chris is..............

a 6V transformer when connected to a bridge rectifier will give you sommat more 'an 6 V DC. output.

[vtsteam]

Here, a picture is worth a thousand words.


This is for a simple transformer -- and according to Bluechip you can eliminate the capacitor as well.

Or if using a center tapped transformer, you don't even need 4 diodes, or a full wave bridge package. Just two diodes (I believe, or is it 1?)


The only problem with all of these, as you say Chris, is, they aren't adjustable. But if they're right, you're good to go

[Bluechip]

Not if you omit the capacitor. It'll just see the rms .
 
It will actually be a bit more than 6V rms with a 50VA tranny 'cos 50VA is a bit over-rated for the job.
 
It will be up a tad because of the favourable load regulation.
 
Not looked but I would guess the load regulation would be about 10% with a 50VA tranny ..
 
   time for me .... as one J Reeves once said 'I hear the sound of distant Becks' and I don't intend it to be distant much longer ...
 
Dave BC
 
 

[awemawson]

The simplest solution in my opinion is a suitable transformer, followed by a bridge rectifier and capacitor, followed by the pwm unit Chris has already bought. This way as he builds the penny pusher he can adjust the speed to suit. The speed will depend on the load and this will probably change as the design develops, so a fixed speed solution is not a good idea. Build a little 'post design design' into it for later tweaking !

[raynerd]

Hello chaps.... I think what you are failing to realise is that I haven't got a bloody clue when it comes to understanding electronics!!!!  So David,

You seem to be looking for the most abstruse solution you can devise to a non-problem   
 
AS Bill Todd, VTSteam et al have alluded ..
 
Get a 0-6 0-6 50-ish VA transformer, nail it to a 15A bridge rectifier, switch on, slide off for a pint while you leave it to ekkle.

So although I appreciate this was said in fun and honesty, without a clear guide as to exactly which transformer to purchase,  which bridge rectifier and exactly how to glue it all together I'm useless and it is likely to go pop!!! 

I suppose my suggestions have all been ideas based on purchasing a psu or converting an existing psu I.e the ATX supply!

I do appreciate all the info so please keep it coming!! I'm in a caravan now until Sunday so no more progress tomorrow. Time to think and decide on exactly how to power it.

I do also agree with awemawson - I'm not 100% sure what speed is best so using a Pwm does provide some flexibility but accept with the problems it is causing, it just adds another problem!!!

Hummm...tricky!

[vtsteam]

I had a feeling Chris needed more than just generic advice.

Okay, Chris, I'm going to vote for the very first thing you asked about, not the PWM Controller you have now, but the one on Ebay, that you first mentioned and I also have, and that I have connected to an ATX PSU, which you also have and seem to be familiar with. And I have run it with a windscreen motor.

Now, since this outfit has already been tested with a windscreen motor, since it is cheap, and uses your available parts, and you only have to buy one thing, that controller, as opposed to a bunch of things -- transformers, rectifiers, capacitors, it's easier and doesn't require building something.

Also, since the pwm controller you have now isn't satisfactory, put it on the shelf for some other purpose, or return it for more than the Ebay one costs, and smile all the way to the bank!

Now if you do this, please make sure that your ATX power supply has at least 8 amps available on the +12 output, and you will need to do a couple thngs to it to make sure it comes on, and has a load on the 5 volt line, as someone else mentioned earlier. But that's not hard to do. And we can help with that.

[raynerd]

  have ordered the new pwm controller and will get onto sorting an Atx supply on Monday!! :-)

[vtsteam]

Maybe you already know how to rig an ATX power supply -- I seem to remember that you did a motorized spindle once -- did that use an ATX?

Anyway, the two things you need to do are 1.) make a connection to the power supply's switch line to tell it to turn on. And 2.) put a load on the 5 volt side so the power supply has something to sense and regulate. Usually that is a power resistor.

However, I'm guessing that you are going to want lights in your arcade game, so why not use the 5 volt lines to power those?

Then  you won't need a power resistor as a load on the 5 volt side -- the lights will be that load. Whether incandescent or LED just make sure they will be comfortable at 5 volts. Probably 6 volt automotive lamps (if you can still get them there  -- we can here) will probably work well enough. Or hook up LEDs so they can handle 5 V. Some can, lesser ones can be hooked in series, or have a dropping resistor, etc.

If this sounds like a lot of jargon, just ask, and we can walk you through it. If not, you're on your way....

[raynerd]

Hey Vsteam, thanks for the details. Yes, I've hooked up a good few different ATX supplies for various CNC machine axis and the spindle as you mentioned. Good point about running the LEDs and lighting off the 5v line.

Just some progress on the mechanism

[vtsteam]

One more thought Chris, and others could probably correct or amplify this, I think you will need a certain minimum amount of current draw on that 5 volt line to keep the power supply healthy.

LEDs are usually pretty efficient. And if you use low power ones, and not very many, there might not be enough current draw between them to be a good "dummy" load. Incandescent bulbs on the other hand tend to be more wasteful, and draw more current, which in this case is maybe a good thing. Whichever you choose, try to draw enough current to equal what the usual dummy load resistor is on these conversions.

Perhaps someone else can suggest a reasonable current draw minimum.

[raynerd]

It is a good point since I expect when I initially want to test the supply on the motor I won't have any LEDs at all. I'll load the 5v line as I usually do with a resistor initially.


Just got back out of the workshop and very chuffed. I know it seems insignificant but I've been having a hell of a job sourcing some tiny slides. It isn't critical enough to use proper linear slides and bearings and too pricy. I've wanted to use a ball bearing draw slide but they are too long. Went to BQ earlier and there was one lone 12" slide, too big for me but it wasnt in a packet of a pair. Decided to ask if they would sell it me and they asked for £3!! I've spent many many thousands over the year but I have never walked out thinking I'd got a good buy ..... A first time for everything.

Anyway, I chopped it in half tonight.  Stripped all the 3 segments apart, ground off any stops, removed the bearings, removed and disposed of the outer extension (telescopic 3 section and I only needed 2 sections), cut it in half and re-assembled.

Two really neat, mini slides!

[mattinker]

Chris,

I thought you might be interested in these :-
http://uk.farnell.com/hamlin/59140-010/sensor-magnetic-spst/dp/1839038?Ntt=59140-010

They are magnetic switches, when approached by  a magnet, the switch closes, they are very easy to set up when compared with mechanical limit switches. They will switch a relay or light diodes. Given as 10watts at a maximum of 200 volts they are pretty flexible.

Regards, Matthew

[raynerd]

Hey Matt, they do look interesting, do you have a specific use in mind with relation to this project.

Got a moving table. It will need to be rebuilt as the link arm is too long and wasting far too much space.

[awemawson]

Chris,

Have you considered the not insignificant weight of a table of pennies or 2p pieces? The frictional load will be quite a bit I suspect as it pushes forwards. The actual movement of the pusher is somewhat less than on your prototype.

Don't forget that when the pennies tip over the edge in the commercial machine, a portion of the 'haul' is split off by a divider so the punter only gets about 75% of what falls - the remainder re-circulates.

Andrew