Power Supply?

How 'bout a VARIAC, a step down transformer, and a bridge? Smoothing caps aren't really practical for 10 Amps, but they won't hurt. Motors really don't care much about perfect DC, 'cause their mechanical momentum (flywheel effect) takes 'em through voltage variations like it didn't even vary.

Variacs are pretty expensive aren't they? I'm trying to keep the cost down. I have a power supply I got from work that is 24VDC 12A that will work, I just need to make it variable. I think that would require a 300W device which is also costly. Any thoughts on making my current supply variable?

See if you can get one of these kits from Jaycar electronics it will handle 30 volts and up to 40 amps if you fit the extra mosfet or a single mosfet with large enough ratings.

Just wire it in front of your 24 volt 12amp power supply and away you go piece of cake

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CAT. NO. KC5225 RRP $23.95 CLICK TO ENLARGE

10A 12VDC Motor Speed Controller Kit

Refer: Silicon Chip June, 1997
Use this kit for controlling 12V DC motors in cars such as fuel injection pumps, water/air intercoolers and water injection on performance cars. You can also use it for headlight dimming and for running 12V DC motors in 24V vehicles. The circuit incorporates a soft start feature, which is used to reduce inrush currents, particularly if the kit is to control 12V incandescent lamps. As presented, the kit will control
loads up to 10 amps, although the addition of an extra MOSFET transistor will double that capacity to an amazing 20 amps.
* Kit includes PCB plus all electronic components to build the 10A version.
* Extra MOSFET available separately, ZT2450.

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I looked it up online and it looks ideal. I can use my 24VDC power supply and build one of these circuits at every drivers station allowing each person to set there own voltage. For a race, all would have to be set the same. For the kids, I can wire in a switch that will throw between the variable resistor and a set value. I would rather have one control device for all 4 lanes, but varying the 24VDC 12A needs a higher wattage device costing more than 4 smaller independant circuits. At least those have been my findings so far.

Torroidal transformers are nice, but for this application, overkill. A regular old style transformer maybe a little larger for the same power output, but a lot cheaper.

If you want cheap...maybe you could try something real dirty but cheap (and I know you guys like it real dirty and cheap )...like a light dimmer on the input to the transformer?... the wattages are probably ok...It may just 'not work' I've never tried it .. I'm sure someone here will have tried it.

The 'proper' way to do it would be to pulse width modulate your DC output.

Del

You know what I would try...

Go get an old 1/2 HP AC motor. Get one of the many cheap triac speed pots. Get an old DC PM motor. Couple the shafts. Speed it up and see what you get. Might be a fun Saturday project.

I have used KepCo on numerous projects. Very flexible and reliable products.

Try this link- I do not know if their pricing is cheaper than what you have found elsewhere (I just spec them-manufacturing purchases them)

http://www.kepcopower.com/rkwp.htm

Good Luck

Are you sure you need that high of a voltage and current capacity?

I'm running slot cars too. The HO size work well on just 18 volts. The older T-jets with pancake motors needed higher voltage to really fly but its actually harmful to them. The newer style with horizontal motors needed LESS voltage and still flew.

Try a 24 volt transformer with at least a 75 VA rating, or parallel ( 2 ) standard 50 VA transformers and then rectify it with a 5 amp rated fullwave bridge. You can go to any air-conditioning contractor and ask them for a used transformer or two or three. They throw them away all the time, they're in every piece of equipment. These transformers actually produce 26 - 28 volts unless you load them heavy.

Those specs were recommended to me by other racers, so I just used those numbers. I'm going to use a 24VDC 12A supply that I can get all the parts to here at work for cheap. I just want to make sure I can lower the voltage for my 4 kids. As for current, I'm using one supply with multiple power taps to the track and I wat to have "plenty" of power everywhere on the track with 4 cars running. Yea it's overkill, but at least it's not too little and I have to go bigger in the future.

Can't offer much practical advice, since I've been away from the hobby for...mumble, mumble...years. But not so long that I don't remember enuff to second you on the overkill. Far and away better than UNDERkill! Besides, the previous posts provided more than enough ways to make 'em go roundy-round!

LM317 voltage reg with 3055 transistor w/heatsink (to boost I) good for 1.2-37V 15A very common circuit free plans all over in internet should be able to build it for under 5$ w/o transformer

icjr

Thanks, I'll look into it.

I'm having a hard time finding anything linking these 2 devices, might you be able to supply a link? Thank you.