Slot cars power supply help.....

[Newpaltzwonder]

Hey guys,

This is probably a simple question......

I decided to dig out my old slot car track and see if it still works....Well it doesn't...the power supply is shot.

Now, the Question....I need to replace the PW, I just want something that will run the cars without killing them. These are the specs on the Power Supply.

The input is: 120 VAC @ 0.12A 60 Hz
output: 22 VDC @ 7 VA

I have a Power Supply that is 13.8 Vdc @ 3 amp, 4 amp Max. I was thinking of using that instead, but I just want to know is there a diffence between VAmps & Amps?

Any help would be great!!!

Newpaltzwonder

 

[officeboy]

Yes, there is a large difference. Well er, actually there is no difference if the voltage is 1 but anyways...

V= volts and VA=volt*amps
so your 7 VA powersupply is ~.31A

That 13-14V transformer should be plenty of juice for your cars.

 

[li_gangyi]

well...but there is one small thing that you overlooked..the original PSU outputs 22V instead of 13.8V...

 

[Brian Donaldson]

When I was young and had slot cars, I added a button to my controller that when pushed it added a second PSU in series and gave the car 48V. I liked doing burnouts. 6-8 V will move them around. The more volts, the more amps they draw and the faster they go.

 

[roddyama]

They are just little DC motors with a rheostat. They'll work fine with 13-14V. We used to use a car battery with a trickle charger.

 

[li_gangyi]

hahax, yeah I remember them...the trick was to slow them down adequately during turns and push them hard during straight,s. Once I had a race with my brother and I sortof cheated by modiifying my track (had a slightly higher voltage), he was going like, huh?? how did ur car go that fast?? then he switched tracks the second round and well...you can guess what happenned...I suppose the 13VDC PSU would work...but since he asked for a 22V one...why not give it to him?? Perhaps a simple SMPSU after the 13.8VDC PSU would be good, take a look at national's line of simple swicthers...or maybe we can add a multipiler to the transfoer to get 2x the voltage??

 

[Brian Donaldson]

You're making this much too difficult. Use a 25V transformer. Rectify and smooth. Then a mosfet follower off of a 10K or greater pot. Maybe you can get a little wheel spin.

 

[li_gangyi]

I did thought of that...well...if he wants to get a new trafo then go ahead...a 12-0-12 or a single 24VAC would be good...get a 500mA one...the smaller 300mA is a bit expensive...supply and demand perhaps??

 

[Brian Donaldson]

If it was mine, I would go for 40V 4A or so. you can always reg it down, but I would want to make smoke, for $hits and giggles

 

[Newpaltzwonder]

Thanks a lot guys!

Wow, I didn't think anyone cared about slot cars...Glad to bring back the momories.

For now, I'm going to use the 13 volt power supply while I look into getting another transformer.

I always wanted to see if I could smoke the tires on one of them, so maybe I will try to get a bigger power supply.

Does anyone have suggestions on where to get a good transformer? And info on how to regulate it.?

Thanks again,
Newpaltzwonder

 

[li_gangyi]

since the cars draw less than an amp..you can use a "normal" linear regulator...such as one based around the LM78XX series..but of course you only have an option of up to 15V...which sucks...you could try raising the voltage with a zener to it's ground pin...which in theory would be as big as the value of the zener plus 15V...if you're using a 7815...OR...you can try a simple Zener transistor regulator...taking stuff to the next level would be using a small SMPSU to regulate the whole thing...try this page
http://www.national.com/appinfo/webench/power/SS/SS.cgi?flow=power&step='1A'
just enter your needs and it pumps out a complete schematic and parts list...of course it would be more complex then a simple regulator...but I like the idea of losing less energy in the process...the speed controller could also be intergrated into the SMPSU so when you depress it, the SMPSU would pump out less voltage...something like that instead of the existing way, which is to burn off the excess stuff and generate heat in the process...transformers can be procured at most electronics stores...RS and Farnell carry lots of them...but at a high price...I suppose you guys have Radio Shack or something like that...I'm in SIngapore, so I can't really help you with htat one...