[Chicane Raceway]

Hiya, following advice and a diagram from people on here I built a brake and Ohm adjustable box for racing, took it to our "local" track for the first time yesterday did half a lap before smoke errupted from the box! looked inside and the wire from the controller had managed to ( im assuming as it wall well soldered the last time i looked!) un-solder itself under im assuming the heat of whatever burnt out!

Any ideas why this happened?

The diodes are maplins IN5817 1A Schottky diodes.

the cars im using are around the Slot It Flat 6 and spirit 26k sillhouette etc area.

Any help would be great im hoping ive just done something wrong!

Kris

 

[RichD]

I expect that something got shorted out. You might have posted a diagram of the circuit, I have never seen a brake adjuster that used Schottky diodes. I use a rheostat to adjust the brakes. It is best to test things with an ohm meter before you connect to the track.

 

[Chicane Raceway]

Ok Rich, I was following a design posted top me by another, its the same as this one here ( the brake bit anyway!) > http://www.chaskeelingscd.co.uk/building_your_own.htm

 

[pfj]

Hi, using IN5817 diodes for these motors is fine I use these for my own controller's, are club controller's and others made for other racer's. Rheostat's can be used but are a bit pricey compared to a rotary switch and a chain of diodes, a cold solder and or not enough play in your wires ( presume your controls are in a box), and there's a strain on these can cause a break and a short also you need to have a reasonable air space around any component's even if you use one's higher rated than needed and not to cram it all into too small a place.I know it look's better useing a neat little box rather than a larger one but these can create problem's in themselve's.Just place the controller on a table and take your time following the cable's from handle to control's and checking over your wireing diagram could just be a loose wire that need's re-soldering, keep in touch with how your getting on. phil.

 

[Chicane Raceway]

OK Phil, It is in a small ish box so maybe i'll invest in a bigger one!! will also retrace through all the wires.

Many thanks

Kris

 

[300SLR]

Getting hot enough to melt solder is in half a lap is very serious overheating.
It's difficult to be certain without more detail of exactly what you've got but I'd suggest the box needs checking over carefully, look for something that has been shorted out or wired incorrectly or a component that has failed..
The Chas Keeling link you quote is all about a controller for MUCH higher current motors than you are using, so things shouldn't be getting that hot anything like that quickly even if you have packaged them a bit tightly.

 

[Chicane Raceway]

Ok, it would be nice not to change the box, so far i have traced my way through the diagram and everthing is as it should be except of course this one wire, im not a massive electronics expert so im gonna get someone I know check it over with the correct equipment to see if i have blown anything up!

Will let you all know!

Kris

 

[300SLR]

Come to think of it, one more thing that might be worth checking out. Can brakes and power be connected at the same time.
If the wiper contact can bridge the brake and power band - this can heat up the brake diodes much more than normal particularly if the wiper doesn't return far enough on brake and sits there bridging the gap.

 

[Chicane Raceway]

I'll check that too, im pretty sure that it does not do that

 

[rick1776]

Assuming that you have not cocked up the wiring I suspect that 300slr is right. If the brake band is still connected as the wiper connects to the power you will kill the schottky diodes real quick.

Get a multimeter and place one lead on the power lead and the other on the brake lead. It should read open circuit all the time. Anything less and youre in trouble. Make sure you have the multimeter leads around the right way if you still have the diodes in the circuit.

cheers
rick1776

 

[Chicane Raceway]

Okay, so I'll get it checked a little later, looking at my controller right now and at rest it does not foul across both at the same time, it does of course touch both when leaving the brake band and of course returning to it, if that still causes trouble how do you all get around that lol!

Sorry if all this is stupid im learning as i go here!

Kris

 

[rick1776]

At no stage can the wiper be touching both the power bands and the brake band at the same time. You will kill the diodes real quick. What are you using? Is it a base model Parma?? Get the Turbo model, that way you can just use the brake button independent of the brake band on the resistor barrel. The brake band on the barrel I just use as a resting pad for the wiper button. The brake wire I only connect to the brake button. Taht way you can not have the power and brake on at the same time.

cheers
rick1776

 

[Chicane Raceway]

Yes I follow now!! I do have a plus/turbo that needs some TLC, i hadnt noticed that the brake contact is on its own not on the barrel! I really couldnt get my head around how you were all doing that!

I will put the standard controller to one side and start fresh i thinks!

Many many thanks, I'll update when ive hopefully got some success!

Kris

 

[Chicane Raceway]

Cant do anything to my broken equipment for a day or two, left me wondering, I have seen others using variable brakes on the basic parma controllers, are these using the "pot" version? does this work?

More questions again sorry!

Kris

 

[300SLR]

Yes either pots or diodes (or a combination of the two) work as brake adjusters.
The characteristics are different, but they don't feel that much different to the driver. Some of the real experts try both, some preferred the continuous adjustment of a pot and apparently at least some of them concluded it doesn't make a significant differance which you use.

 

[rick1776]

I use a diode (1N4001) for the first position and then 0.5 ohm resistors for the rest of the pot. Works well.

cheers
rick1776

 

[stoner]

this may be a different subject, but when you have a pot on a standard parma does it just reduce the standard brake to lower values or does it supply reverse power to stop the car on a sixpense, or do you have to go with the digitalised? controllers for that. sorry if it sounds daft, but as you know i,m a moron with electrics. john.

 

[pfj]

Hi, when useing a pot or diodes for brakeing on resistor controller's your only reduceing the output from the motor either voltage with diodes or resistance with pots, to increase brakeing greatly an external power source such as a battery was used many moon's ago due to motor's having poor brake's this has been banned for a very long time ( at least at club and race event's ) but nothing to stop the home racer. When useing pot's for any kind of adjustment you have a stepless control but their track's can be burned out by short's also easy to change adjustment by accident and not realize as opposed to a click stop control such as a rotary switch. phil.

 

[Chicane Raceway]

I worded that wrong, I meant can you use a pot on a standard parma without blowing it up due to the crossover from the brake to the power bands?

 

[300SLR]

Parma pots are quite robust.

Did you say there was smoke coming out of the brake box within half a lap?
If there is a fault that serious, it needs fixing.
It's quite likely a Parma pot would be damaged with that sort of fault.