View Full Version : Power Supplies

25-04-2013, 09:42 AM
Hopefully a simple question regarding power supplies.
If I need approx. 70volts to power four (potentially 5) 80 volt drives and 3.1Nm motors, 24 volts for home and limit switches and 5 volts for BoB. How would you go about designing or buying suitable power supply.

25-04-2013, 06:51 PM
I'd use different power supplies.

You really need the 5 and 24volts active all of the time. You could include them in the E-stop controlled circuit, but if they're only used for control purposes, there's not really any benefit in doing so, provided the E-stop cuts power to anything that provides movement.

For the drives, go for a torroid (50VAC theoretically gives 70VDC, but is nearer 80 when you allow for effeiciency/mains voltage fluctuation), suitable bridge rectifier and big capacitor, to create an unregulated supply.

For the 24V, you could use a DIN rail mounted switched mode supply, or go for a small transformer with a 24V linear regulator, but you'll have to use a variable output regulator as 24V is not a common standard output.
For 5V, you could use another switched mode supply, or if required current is low, then just run a 5V linear regulator from the 24V.
You may be able to find a suitable switched mode supply that does both voltages, but I wouldn't know where to look.

If you want a torroid and required parts, I have a 750VA 50V surplus to requirements. This one to be exact - Standard Range Toroidal Transformers: CM0750250: 750VA 230v to 2x50v (http://www.airlinktransformers.com/chassis_mounting_toroidal_transformers_standard_ra nge/3-CM0750250.html), along with a 25A bridge rectifier and 100Vdc 22000uF capacitor. Only use has been linking it all together on the bench to test.
I also have an old school 24VDC supply that came from my new milling machine, which I'd throw in for cost of postage, as I've no idea if it works! The links are set for 100V input, but can be resoldered to 240V.

25-04-2013, 08:50 PM
Using a toroidal transformer for the stepper motors is almost certainly the best option.

I'm might be interested in that transformer if GTJim doesn't want it...

26-04-2013, 08:18 AM
Thanks for the replys.

If the offer is still available regarding the power supply I would be interested. Just PM me to let me know what you want.

How would you go about making a PCB to suit the components for the power supply?

26-04-2013, 03:21 PM
I wouldn't know where to start making a PCB, I just soldered the bits together & then mounted them to a bit of 5mm board with double sided tape so it looked tidy.

26-04-2013, 04:06 PM
You don't need a PCB when using a torroid, as eveything is either screw or spade terminals.
Torroid is held on with a bolt and has loose wires for connection, bridge rectifier is bolt mounted with spade terminals, and capacitor has a bolt down clamp with either screw or spade connectors.

I'll drop you a PM in a bit.