Gallery, Projects and General > How to's
How to Make a Power Supply
Darren:
At last I've managed to put a vid together,
My mobile died, I've tried four others that failed for one reason or another, mostly poor sound or simply won't talk to the computer.... :bang:
So I ended up using a web cam connected to my laptop, mostly held by hand so the vid is a bit jumpy. Then there were software issues :bang: :bang: :bang:
But it's done now :D, I'm no movie maker or commentator so please excuse the amateurishness of this vid.
Hopefully it will answer a lot of questions and throw some light on the matter.
I doubt I've covered everything so any questions please speak up. :ddb:
Enjoy....
Agg...the vid is too long for Photobucket.....oh the joy of computing !!!
Hang on......
Darren:
OK, vid now split into two, hope they don't bore you...... :ddb:
Darren:
A little more playing with this tonight, but first let me show you a better picture of where the two diodes go and their orientation.
We use these to protect the discharging energy from the smoothing caps when the circuit is switched off. Caps are in some ways like little batteries, except they can store quite a lot of energy. Even worse they can discharge all of it in an instant which is what they want to do when the power is switched off. The energy released from the caps will try to find the path of least resistance to dump to. This unfortunately is through the regulator chip. The diodes offer a new path of no resistance thereby diverting any possible catastrophe away from the regulator.
Most manufacturers will declare that this type of regulator has built in protection within, in the form of a diode. Maybe it has, but don't believe it with do as it says on the tin for a moment.
Maybe with lower voltages and currents it would be fine. But not here.
Now that the protection has been added it's time to think about some smoothing capacitors. But first I have added an extension to the neutral/earth rail to assist connection and mounting.
Bottom right of the board.
Now the caps, both negatives connected to the new earth rail.
And from one cap positive to the live bar/regulators input pin (3rd pin)
Positive from the other cap to the regulators output, (middle pin)
Now we have compleated the power supply smoothing and protection circuits.... :ddb:
Darren:
Some of you may have noticed that I have changed the resistor and indeed added another....
The original was 100 Ohms, and the two new ones are both 220 Ohms 1/4watt. When the circuit was first put together I used the manufactures recommended values.
However, as is usual, some testing and fiddling showed that the above sizes give us a closer result to our needs.... :smart:
There are online calculators to work this out for you, but I find a bit of fiddling works best.
Regarding the second resistor on the far left is inline with the adjusting pot, (in series) basically this adjust the lowest voltage output from 1.2V to a more usable 2.5V.
If we leave the lowest voltage at 1.2V what happens when we turn the pot down to slow the motor is that it will stop. This is highly undesirable if you are in the middle of machining and merely wish to slow the transverse speed. Adjusting the values in this way will always insure that when you turn the pot fully down you are at a nice comfortable slow speed setting.
(it also puts far less stress on the circuitry if you turn it down low enough to stop the motor and forget to switch the power off. Left in this state the circuit will become very hot and may possibly damage itself. This way you have to turn the power off to stop the motor)
Finally in this picture you can see that I have added a push to break switch inline with the adjusting pot. It's the one with the red button.
When the adjusting pot is turned to a higher resistance setting this will increase the speed of the motor. Lower resistance lowers the motor speed.
The "push" switch breaks the circuit offering an infinity resistance, ie very high. When the button is pushed the motor will spin at full speed. Useful for rapid transverse.
Let go of the button and the motor will resume to the pot setting speed as set previously.
This is useful not only for momentary rapid transverse of the mill bed, but it also allows you to leave the pot alone when you have found a comfortable cutting speed.
Well that's it, the power supply is done. This will provide 2.5V-34V at 5 Amps. 7-8A if you add a bigger heat sink, but I wouldn't recommend it as there are better ways to achieve this which I shall go into if anyone requests.
All you need now is a reversing switch and a box to put it in........ :nrocks: :nrocks: :nrocks:
Divided he ad:
Fair do's chief :bugeye: You've been working hard on this one today :thumbup:
Very good videos, I think you sound like the guys on the videos they used to play for us to watch in science and engineering in school.... That's not a bad thing, you sound like the guys who used to narate.... Made me want to make paper airplanes and throw them at someone :lol:
I like the use of the oh so silly scope, it allows you to not only show/prove the workings but just looks too damn cool :headbang:
I'm going to need a parts list if you would be so kind, I've got my motor all mounted and ready, Been fitting my new verticle DRO on my Z axis tonight... Slight dramas!! But this isn't the place for that disclosure! :offtopic:
I'm getting my mill up to a good working order DRO's getting there and then just waiting for this circuit to be made and I'll be machining hopefully much more accurate parts?! :)
It is true that :mmr: and that :nrocks: Top job, thank you :thumbup:
Ralph.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version