Gallery, Projects and General > How to's
How to Make a Power Supply
Darren:
Yes we have one of the highest safety standards in the world I believe.
Don't worry about us Brits :thumbup:
raynerd:
If I want to run a driver at 2.5A and 3.75V but ulimately I have three boards to drive 2.5 x 3 = 7.5A - will my PS have to be rated 7.5A or above? It is this link between voltage and current that confused me and the requirements to power components I don`t get. When selecting a power supply to drive the above, am I just interested in the ampage that it can draw and the fact that it needs to draw 7.5A maximum. The voltage will just be adjusted to achieve this current right?
The power supply that they actually sell for this setup is rated:
--- Quote ---Small Power Supply for our 2.5A 3 Axis Driver Kit.
Input voltage of 100-240V; AC 50-60Hz; 1.5A
24V DC Output
Short circuit, over voltage and over current protection.
24 Volt Power Supply £33 Each + £6.50 P&P
--- End quote ---
One last thing, to throw a spanner in the works, if I only wanted to run one 2.5A driver would this need to be a variable supply or would it be suitable to plug into one driver as it is?
Any help appreciated.
Chris
John Hill:
Chris, when that power supply is outputting 7.5 amps at 24 volts thats 180 watts but you say your load voltage is only 3.75 volts? 3.75*7.5 =28.125 watts, more than 150 watts going 'somewhere'. I dont think we have the fully story here but at least we can be confident the 24volt power supply can supply the 10 amps just by doing a check that the power supply input watts is comfortably more than the required power supply output watts.
I assume this is a controller board to drive three stepper motors? Can you provide a link to a description of these controller boards?
No, you would not have to change the supply if you reduce the number of drivers. Assuming the voltage stays the same the amount of current that will flow will increase as the load units are increased up to the maximum current available from the supply.
Bluechip:
Chris
I would suggest that a 24V PSU for a 3.75V motor is not suitable. You can put dropper resistors in series, but is is a very inelegant way to go about it.
There is not enough info. on the stepper motor, but here's a quick ball park guess .. lot of assumptions tho'
24 - 3.75 = 20.25 V to be lost.
Assume motor load = 2.5A ( & constant, which it won't be)
Series resistor = ( R = ( E / I ) 8.1 R
Power to dissipate = I^2 x R = 50W
Thats a lot, it will get hot.
If I were doing this, I would not go with that PSU. It doesn't really come close to what is reqd.
John. If the PSU has effective current limiting, you wont get 7.5A out of it. I presume if it's designed for 2.5A, the internals would be stressed at 7.5A.
I would make my own PSU, (do a Darren :D, )with my favourite Reg. ic, the L200, with a series pass transistor.
This chip is a variable output from 2.7V to 37V at 2A, more with a pass transistor.
Try looking for L200.pdf
Lots of circuits thereon..
Dave
raynerd:
Ok - I`m sorry but still some of this is going over my head:
The driver:
http://www.routoutcnc.com/singlesmall.html
The motor:
http://web.archive.org/web/20050318040147/http://www.homeshopcnc.com/page3.html first one on that page but now wired 4 wire bipolar.
The ""available" power supply -
http://www.routoutcnc.com/hardware.html - down at the bottom - the 2.5A kit PS, not the others.
I don`t want to go with their power supply because I have a feeling that this driver, and I only have one at present just to try it, won`t be good enough to drive my motors or it will be good enough but the motor won`t be! Basically, I think I`ll end up upgrading! I want to make a PS so that I know how to go about upgrading in future, to save money (hopefully) and also so that I have a better understanding...
So i I had a go at making Darrens power supply - would it work as it and what "settings" would I need it on to power first of all just one motor and driver and then eventually 3 motors?
Chris
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