[Intergrali]

Anyone got the Rapid lectonics catalogue from march this year? look under power supplies there is one than can be run at 15V with 40A flowing through it..

only 90 squid buys!

Rob.

 

[Tropi]

Thanks very much for the reminder, Inte.
It's time I actually purchased one of these, even though I currently have no working track at home.
Got to plan for the future.

This unit is available in both 25 and 40 amp variants and, as far as I can see, is the best value Power Supply Unit readily available in UK. (The US guys get much better deals)

For those interested, here is the Rapid Electronics PSUs link, which gets you a largish PDF document and the particular unit is, about three screens up from the bottom of the document.
Later Edit: IF that link no longer works, (revamp of Rapid Electronics' web site) then please try THIS ONE

Order codes are
85-1824 for the 25 amp model
85-1828 for the 40 amp model
Voltage is variable over 3-15 volts, with an additional fixed mode of 13.5 volts - a sensible standard figure for slot racing, but with the facility to vary if you prefer.

 

[Doug]

I recently purchased a power supply (0-18V). It only starts to do it's thing at around 16 V. This one you're talking about (3-15V) may be a little under what some of these cars require.

 

[Tropi]

It sounds as though there is something wrong somewhere, Nuro.
Maybe a fault in the PSU?
These motors shoud run fine on as little as 12 volts, which used to be the standard figure. But, if amperage is lacking or bad connections anywhere, this would have a detrimental effect. The usul reason for poor performance is lack of amps rather than lack of volts. Are you in a position to meter the circuitry to see what is really happening?
Our own Graham recommends these particular PSUs and it is only due to him that I even know about them - he has tremendous knowledge of all things technical!

 

[Intergrali]

oh I was just being silly.. 40A would fry an S can wont it?

(it's been a long time round here since one of those went a bit spectacularly!)

Rob.
p.s might just get one as 25 amp is only 60 smackers!

 

[Tropi]

QUOTE p.s might just get one as 25 amp is only 60 smackers
Actually £69 plus VAT = £81,
but that's as good as I know of for anything similar in UK.
I envy the USA guys who can find this kind of stuff at around 2/3 the price or even less.

 

[RichD]

These power supplies are cheaper than you would ordinarily see because they are switching, rather than linear power supplies.. The rated ripple voltage, which is the unwanted AC component of the output is a little high. An extra capacitor across the output should remove most of that. If you have to crank your track voltage way up you need to take some measurements to find out what is really going on. If you were to put a car on the track with something under the back of the car to get the wheels off the track you could punch the controller and measure the voltage at the track rails. An open circuit voltage won't tell you anything except that some sort of power is getting to the track.

 

[Tropi]

Rich, which are you referring to?
The quoted Ripple & Noise for this particular one is 50mv - It sounds low to me, but I know that I don't know enough to know whether that is good, average or bad!

 

[RichD]

The rated ripple for my power supplies is 1mV. I suspect that is less than you would normally see. 50mV might not be enough ripple to cause any problems, but the price of a 4700 MFD capacitor is cheap insurance.

 

[Tropi]

What power supply are you using Rich?
It would be good to get as much info into print here as possible.
We could all benefit, esp me!

 

[RichD]

I have a pair of Lambda LQ 531 power supplies. They are laboratory grade instrument power supplies that cost $850 each back in 1985. I paid $100 for the pair of them, otherwise they would have ended up in a dumpster.

 

[Sidecar Steve]

Hi Guys. I'm after a little bit of advice on a power supply. I've got five wall warts (one per lane plus one for a lane management system). I spotted this in an electronics store and it seems to match up with the thread above. Here is the sales blurb:

3-15V power supply with up to 25A continuous capability at 15V (lower current at lower output voltages).

Inbuilt metering for output voltage and current with extensive overload protection added, such as a Tri-filar transformer winding, high-temperature transformer components, 50A bridge rectifier, rear-panel mains circuit breaker, and a transformer thermal fuse.

High-current banana-style and low-current output connections

Internal heatsink and thermally-switched fan

Metal case (320 x 150 x 145mm)

Duty cycle = 100% for all rated output voltages and respective output currents.

Load regulation = typically <100mV drop between 0 and 20A loads at 13.8V or 15V output. Less than 130mV drop between 0 and 25A loads at 15V output.

Line regulation : For 240V a.c input, varied +/- 5%, regulation is better than 0.1%.
Ripple and Noise = typically <1mV (with 25A load and 15V output).

Does this sound like it is suitable for running fly cars with magnets on scalex classic/scx track?

Steve

 

[Fergy]

The specifications look quite good and your Fly mag cars should be quite happy with this unit.

Personally, I would like to see the output go to 16 or even 18 volts (just for some added "headroom") but that's just me and it's not a nit-pick at this supply. I also prefer screw terminals for the outputs - in fact, I'm not sure I've ever seen banana-style connectors over here rated at 25A! ...maybe our bananas are lower quality...

Bottom line: Sounds good, and the output is more than adequate and therefore just right!

 

[JOHN SECCHI]

Hi All
The Luton slot car club [ex Vauxhall club] have purchased 2 of the 40 amp Rapid switch mode variable power supplies with the intention of replacing the ageing 12v car batteries/chargers on there 4 lane BSCRA track. As a way of a test , one of the supplies was wired up to 2 lanes [at a fixed 13.8v] and the other 2 lanes remained on battery/charger supply. A nights racing was run using a mixture of Gp12 and Super 16D powered cars and very little difference was found between the lanes [my impression was that the power supply felt smoother!] and all went without problems. As a final test two 1/32 BSCRA sports cars were run on the power suppy lanes [winds used were 27 turn of 27 AWG and a 28 turn of 26 AWG] the cars were put on the start line and the track was powered up as per a normal race, the supply coped without fuss and it was noted that the combined cars drew about 25+ amps draging down the straight together but no stall reading was taken as the meter reaction time was too slow, however the overload LED did flash.
The single supply will remain for a month or so to gauge its reliability and if all is well then the second supply will be installed.
Oh, and by the way i have ordered a 25amp supply for myself, 3v min is a pain but i will be able to run a load of accessories like tyre truer, com lathe, strap motors Etc Etc without problems and it's cheap!
[oneofwos]

 

[Intergrali]

yeah, thats the thing that got me, only 15v max, we run 16.5 minimum at the mo and upto 18 on one of the middle lanes

Rob.

 

[Mecoprop]

It's VERY reassuring to see a calm and factual endorsement like that from a well-known 'old-timer' who has all the requisite experience to make a dispassionate judgement that the rest of us can trust implicitly.
Cheers John!