Step down adjustable power supply

[michael howarth 1Participant @michaelhowarth1]

MichaelG…yes, still working on it but just got back from a lengthy trip to see a v. sick relative….and before that my multimeter ammeter in the appropriate range went on the blink…so a bit of catching up to do.

Mick

Broadband just went on the blink as well, hence two posts for the price of one.

Edited By mick H on 21/08/2014 17:23:57

[michael howarth 1Participant @michaelhowarth1]

I connected up the step down adjustable module (the 99p one) to my 12V power supply and thence to the screwdriver powering the filing machine and on reducing the output voltage to 4V achieved the desired 80 strokes per minute. After 10 minutes continuous running, there was no discernible strain on the motor and no discernible heat from it either. There was plenty of power for filing in as much that it was not possible to stall it. I have no idea what current is being drawn except that it is more than 500mA. I will discover that when my new meter arrives. The processor on the module does get pretty warm which is probably not good… but is ok with a block of mild steel on it as a heat sink!

I think I shall lash out and buy a 10 amp PWM module for £2.50 or thereabouts whereupon, hopefully, there should be no problems at all. The contributions to this thread have been really interesting but often over my head I am afraid but I hope that it will have been of some use to others.

Mick

[Michael GilliganParticipant @michaelgilligan61133]

Well done, Mick

Thanks for the update.

MichaelG.

[Ian S CParticipant @iansc]

Perhaps an aluminium heat sink on it might do the job.

Ian S C

[MuzzerParticipant @muzzer]

Note that the LM2596 controller used on this module seems to be automotive rated ie -40…+125C case temperature rating. The pain threshold for most people is in the 50-55C region, so it may be fine as it is. Does a droplet of water on the device boil away after a few seconds?

In the limit, if it gets too hot it will simply inhibit the output until it cools down enough. Cooling the black resin surface won't make any noticeable difference – you'd need to be cooling the copper slug that's in contact with the board. Of course, these things are designed not to need much heatsinking….

Murray

[michael howarth 1Participant @michaelhowarth1]

Ian/Muzzer…..I gave the thing an extended run of over 30 minutes and most strangely the processor only heated up to around 35C as measured with my infra red thermometer! I also measured the temperature of the motor casing and that was just 5C over the ambient temperature.

May I take this opportunity to ask where I might source small 2 pin plugs/sockets which could be used in the 12V 5amp type circuit?

Mick

[Keith LongParticipant @keithlong89920]

Mick

I'd start by looking to see what your nearest car, caravan or boat accessory shop has to offer for the plugs/sockets. generally the ones there will be for 12V at the sorts of currents you're looking at. After that then any of the electronic component supply houses will have suitable items. DON'T be tempted to use anything normally found on a domestic or industrial mains ac supply – they'll work OK but give the possibility for some pretty horrible accidents if someone plugs things into the wrong outlet.

[Ian S CParticipant @iansc]

Here in NZ there doesn't seem to be the range of low voltage plugs and sockets that there was 30/40 years ago, I'v even ended up making my own.

Ian S C

[Keith LongParticipant @keithlong89920]

Another possible source of suitable plugs/sockets for 12v at a few (a good few!!) amps is a model shop that deals with radio control. The modern motors in planes, cars and fast boats pull high currents and all from low voltage battery packs.

[MuzzerParticipant @muzzer]

You could look in Maplin if there is one near you. If you order from them online it may be with you next day unless the service had suffered recently. Or try Rapid Electronics, CPC Farnell etc. Those coaxial power connectors used for phones and laptops may be just what you need. There are several different sizes so you'd want to make sure you got a mating pair.

Murray

[michael howarth 1Participant @michaelhowarth1]

The screwdriver motor draws 1.5amps at 4Volts.

Mick

[Neil WyattModerator @neilwyatt]

Try Tamiya battery plugs. These are excellent for high current applications and have locks so they don't come free under vibration.

Neil

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