Assistance please to select a suitable power supply

[John HinkleyParticipant @johnhinkley26699]

In order to complete my die filer project, I have recently purchased one of these to fulfil the requirement for a much reduced spindle speed:

It is a 12V DC motor driving through a compound gear train to give 120rpm output. I also bought one of these to power it:

Having connected the latter to the former (ensuring maintenance of polarity), I switched on the supply and the LEDs lit up. On advancing the voltage knob, the display voltage indicated a slow rise for a couple of seconds, then everything went dark. No movement of the motor was detected, so I assume I've damaged the power supply somehow. I'll try again with a battery charger to test the machine, but I'd rather have some form of variable voltage to control the motor's speed. Anybody out there care to suggest a suitable and robust power unit, off-the-shelf and preferably around £10? I've obviously looked on the usual marketplace sites but they are either too elaborate for my needs, or wall wart style with no control. Would one of the widely advertised PWM units for LED lighting be OK? It needs to supply 12V DC @ 3A max from 230V AC mains input.

Thanks in advance,

John

[John HinkleyParticipant @johnhinkley26699]

[John HinkleyParticipant @johnhinkley26699]

It's resolved, now chaps! Turns out the mechanism I was trying to drive had sort of gone over-centre and therefore locked solid. Once I'd identified my problem and rectified it, it transpired that I'd mistakenly ordered a 24V supply instead of 12V – result – magic smoke from the motor and another order for a geared motor and and new power supply for 12V to be on their way. That'll teach me! Well, it probably won't, 'cos I keep making silly mistakes these days. Better get the grey matter checked out, methinks.

So, no need to reply with your suggestions, rude or otherwise, thanks.

John

[John HaineParticipant @johnhaine32865]

It would have been good to make sure to buy a PSU with in-built current limiting.

[John HinkleyParticipant @johnhinkley26699]

Seems that I was a little previous with my death sentence on the power supply. Just for fun, I stripped the gearbox for a look see and connected the motor to the power supply (before I fried the motor) and it worked for a while. That's what lead me to investigate why it stalled. After the smoke had subsided, I disconnected the power supply and checked the output with my multimeter. Still giving good volts, albeit too many. New motor/gearbox and 12V power supply en route.

John

[BufferParticipant @buffer]

Your die filer project sounds like a great MEW article to me.

[Martin KyteParticipant @martinkyte99762]

Sounds like you fried the regulator part of your power supply.

I would suggest that people who do this kind of work invest in a bench power supply to make life easier. You get  adjustable voltage, current limiting and a read out of current and voltage when running. Once you have set up and tested whatever cct you are building then you know exactly what to specify for your final supply.

regards martin

 

Edited By Martin Kyte on 30/09/2022 19:38:27

[John HinkleyParticipant @johnhinkley26699]

Martin,

I agree that would be ideal. However, I designed and built the filer as a result of a question on the forum and look at it as a bit of a CAD design challenge and the basis for a series of videos. I fully expect to use the thing rarely, if ever. Just another useful tool that I'll never use, along with all the other "exercises" that I've made over the years.

Buffer. Thanks for the compliment, but it really is a bit of an over-engineered re-invention of the wheel. The only difference between my design and that of a conventional filer is the variable stroke and stroke rate that mine provides. Insufficient reason, I think, to warrant an article submission.

John

[Nigel Graham 2Participant @nigelgraham2]

I'd be inclined when building any low-power d.c. equipment or accessories, to add a fuse between the PSU and motor, too, rated to protect the PSU.

Not use it very often, after all that work? I reckon you'll find all sorts of applications! Could such a machine also be fitted to accept suitable saw-blades?

[Robert Atkinson 2Participant @robertatkinson2]

Talking of fuses, what sort of mains plug was fitted to the power adaptor you bought?
All the similar ones I found have clearly illegal and unsafe mains plugs. Specifically no fuse and partially shrouded earth pin. These plugs ate typically narrow at the top like a upside down fat T.
Generall these power supplies a low quality. unreliable and potentially fatal.
You are not going to get a safe and reliable new adjustable 36W supply for £10.

A better option might be to get one of the low voltage PWM DC motor cotrollers from ebay and the like and use a quality external mains to DC supply. I'd pick a >5A PWM controller and a separate power supply. An old laptop supply or a 13.8V fixed bench supply mabe for CB radios and the like would be options. Any voltage from 12-16V would be OK. Having it external means it could be shared across several projects.
A completely random example of a PWM controller is http://www.ebay.co.uk/itm/164646133052 While this looks suitable I'm not recommending it or the supplier, it's just an example.

Robert G8RPI.

[Author]

Posts