Mains power supply for 12v dc motor

You don't need anything that fancy in reality. JJust a 12V transformer and a bridge rectifier will d just fine for running a motor. A 100VA 12V transformer will be big enough for intermittant use and a 150VA one for constant duty. A 25A bridge is recommened they are cheap enough.

Robert G8RPI

My 3D printer uses a PC power supply with a couple of power resistors to keep it happy. One nice thing is I added a switch in the standby circuit.

For my astro I have a nominal 12V 150W psu like the one in SOD's post. I deliberately went for one greatly over-rated for my needs. I run it at a higher voltage to mimic a car battery then have two switching regulators to give me 12V and 5V for other devices.

Neil

Ho hum, should have asked here first, still, I think there is room for it in the "bound to come in useful eventually " box.

William.

Good point, whilst old-fashioned battery chargers are simple beasts that don't care about the load the same can't be assumed about today's magic boxes. I've not taken one apart yet, but a fast-charge unit I looked at in a shop recently was too light to contain a hefty transformer. As with wall-warts, I suspect transformers are being replaced by switch-mode power supplies, and once that's done it's trivial to specialise the electronics to do proper battery charging.

So a new battery charger could well be a close relative of a LED PSU with the added disadvantage of throwing a wobbler if the load doesn't behave like a charging battery. Although a smart charger refusing to run a motor properly because it's profiling volts and amps might be seen as a step back, at least the new one is clever enough not to damage batteries as is possible with a simple transformer/rectifier. Maybe!

Dave

When making my original suggestion, I assumed [based on its declared purpose] that the motor would only be used intermittently. In which case, I was thinking of a battery somthing like this: **LINK**

https://docs-emea.rs-online.com/webdocs/16c3/0900766b816c34e3.pdf

... Which can be kept on permanent trickle charge.

Is that unrealistic ?

MichaelG.

Hi.

Thanks for all your responses to date. I have not been ignoring you all but have been inwardly digesting all the comments. I am learning a lot from it all.

One thought which has come to mind is that if a 20amp led power supply objected to the high inrush current of a motor would it improve things if a variable resistance was wired in series with the motor to give it a soft start. So long as I always remember to use max resistance at start-up.

Or alternatively one of Geoff's suggested speed control devices.

Cheers. Brian