SlotForum banner

1 - 20 of 21 Posts

·
Tel
Joined
·
4,031 Posts
I bought a 12-24v max 8 amp PWM light dimmer in the hope I could use it to set a constant pace car to drive my track.
My track is wired as standard UK club tracks, that is too say as per: http://www.cfrost.host-ed.me/trackbuild/part5.htm

If I wire the controller straight from the psu, and hook a motor to the output terminals, it varies speed as expected, so the controller iself works.
If wire to a plug into the controller plug socket, then it only does flat out regardless of dial position.
I presume this is to do with the way the track has the negative wired, the dimmer has seperate negative in and outs, the way the track is wired there is only one negative.

My question is, is their a way I can wire the dimmer to the 2amp 3 pin plug and put it into the controller socket on whatever lane I wanted to run a "pace" car ?

This is the dimmer I have:



Or is this not possible with this dimmer ?

I had previously been using this, which as you can see has a common negative and worked OK, but now its lost its range of adjustability and its a resin sealed box so I cant even attempt a repair !



It only had a 1.5a rating so I am presuming it got a bit much for it, although it did last for a year !
 

·
Tel
Joined
·
4,031 Posts
Discussion Starter · #2 ·
/ Watches tumbleweeds drift past ...
 

·
Registered
Joined
·
2,183 Posts
just rereading request, have you wired the negative from supply into controllerthen out to track or from track to input then out to supply, if it works without te track then on or the other above should solve problem I think
Zen
Please let me know what happens
 

·
Rich Dumas
Joined
·
3,539 Posts
You can't put this device in the controller circuit, the input side has to be connected to a plus and minus DC voltage source. If you put it in the controller circuit one of the input connections would also be connected to the output. You could modify the track wiring to get the unit to work but it might be easier to use a regular controller with the spring removed.
 

·
Tel
Joined
·
4,031 Posts
Discussion Starter · #5 ·
QUOTE (zendragon @ 26 Aug 2012, 17:39) <{POST_SNAPBACK}>just rereading request, have you wired the negative from supply into controllerthen out to track or from track to input then out to supply, if it works without te track then on or the other above should solve problem I think
Zen
Please let me know what happens

No the negative comes from the plug "earth" pin to enable (literally) plug n play.
I would presume running a seperate negative from PSU to dimmer wouldn't change anything as the same PSU negative is wired "always on" to the track via the conroller sockets.

QUOTE (RichD @ 26 Aug 2012, 17:49) <{POST_SNAPBACK}>You can't put this device in the controller circuit, the input side has to be connected to a plus and minus DC voltage source. If you put it in the controller circuit one of the input connections would also be connected to the output. You could modify the track wiring to get the unit to work but it might be easier to use a regular controller with the spring removed.

Yep, thats what I was thinking, I didn't know if their was a way I could get round it by fitting a component or two in the dimmer ?
Presumably this dimmer outputs on 2 channels due to being PWM, were as the DC converter I used before was happy to share the negative as it is analogue.
But I know you can get PWM controllers, so how do they work it ?
 

·
Registered
Joined
·
2,183 Posts
PWM controllers supply full power at all times, they only alter the speed of the modulation, to exagerate you get a pulse of 12 volts then a second later you get another one, the faster the modulation the faster the engine seems to be running or the less its turned off or at zero voltage.

( If I wire the controller straight from the psu, and hook a motor to the output terminals, it varies speed as expected, so the controller iself works.
If wire to a plug into the controller plug socket, then it only does flat out regardless of dial position.)

You said that this device worked when it wasnt connected to the track, if so then there should be a way of putting it in circuit, it would seem people would rather critic my answer than help with your problem
Zen
Maybe wire direct to the track straight from the psu with out going through a power base if thats how you are doing it now
 

·
Registered
Joined
·
2,094 Posts
The 12V wire usually goes to the barrel of the resistor. This now goes to the input +ve of the PWM. The wiper wire on the controller now goes to the output +ve of the PWM. The brake wire that usually goes to the back of the barrel resistor will now go to the -ve of the input and output as I suspect these are common on the PWM.

cheers
rick1776
 

·
Slot King
Joined
·
2,604 Posts
Without seeing the device, it is difficult to say why it doesn't work when a PWM controller does.

The best way to avoid throwing it away, is probably to wire it direct from the PSU to the track (+ - in and + - out)
Then fit a bypass switch so that you can return to normal control.

Best of luck

Joel

PS: I read somewhere that these light dimmers are not very good at driving motors, please let us know how you get on.
 

·
Tel
Joined
·
4,031 Posts
Discussion Starter · #9 ·
QUOTE (zendragon @ 27 Aug 2012, 02:03) <{POST_SNAPBACK}>PWM controllers supply full power at all times, they only alter the speed of the modulation, to exagerate you get a pulse of 12 volts then a second later you get another one, the faster the modulation the faster the engine seems to be running or the less its turned off or at zero voltage.

( If I wire the controller straight from the psu, and hook a motor to the output terminals, it varies speed as expected, so the controller iself works.
If wire to a plug into the controller plug socket, then it only does flat out regardless of dial position.)

You said that this device worked when it wasnt connected to the track, if so then there should be a way of putting it in circuit, it would seem people would rather critic my answer than help with your problem
Zen
Maybe wire direct to the track straight from the psu with out going through a power base if thats how you are doing it now

I could do that, but I was hoping to be able to just plug it into a controller socket as the old converter was.
The simplest solution (in theory) for making it work that way would be to take power direct from PSU to device, insert a switch in line on the negative before the controller socket, and wire the output to a controller plug so I could use it on any lane.
I don't really want to go that way though.
I didn't make myself clear about PWM controllers, I understand the princible of their operation. What I meant was if they work on a standardized slot car wiring circuit with an always on negative, their must be a way to make the PWM dimmer do the same ?

QUOTE (merkit the grof @ 27 Aug 2012, 08:15) <{POST_SNAPBACK}>PS: I read somewhere that these light dimmers are not very good at driving motors, please let us know how you get on.

I don't know why it shouldn't do the job ? .... It works fine when connected direct to psu and a motor, and has a 12-24v 8A rating, so should be man enough at least to my laymans understanding
 

·
Premium Member
Joined
·
97 Posts
I havn't read all of the replies but don't over complicate things. The easy way is to place the dimmer in line immediately after the PSU using sockets or a 2 pole changeover switch. Then bridge the L & N teminals in a 2amp plug and plug in the controller socket which will allow you to control the voltage to the track. Nothing to do with electronics - just 12v dc wiring. Standard UK track wiring sends negative line to the left strip (with a link to E terminal for back emf braking) and the positive line to the L terminal where the current goes through the controller and the out via the N terminal to the right strip. So, by linking L & N terminals you are sending the controlled output from source (dimmer) straight the the track.

Simples(I think)

Take care
**** L
 

·
Registered
Joined
·
2,756 Posts
Unless it has been stated before the basic problem is that you were trying to feed power from two different sources at the same time. If you fit the stated changeover switch(es) and use the tracks +12v supply you will eliminate this problem and it will work as envisaged.

I think?
 

·
Tel
Joined
·
4,031 Posts
Discussion Starter · #12 ·
You both have missed the point, I want to be able to use the dimmer in any one lane and a controller as normal in any others.
I don't want to change the track wiring, I want to know if its possible to modify the pwm dimmer in such a way it can be plugged in like a pwm controller.
The key point is the always on negative which the dimmer wants an in/out for. I need to get it to work without a seperate in/out on the negative, like a controller, if possible.
 

·
Tel
Joined
·
4,031 Posts
Hi Rick1776,
Yes, that is how I wired the dimmer initially, but it only outputs full power to the track, presumably because the pwm dimmer has seperate -ve circuits for input and output.
I have tried wiring negative to dimmer input, then output, then bridging, result is always full power at track.
Pwm controllers must allow for a common negative to work, what I am trying to find out, is if their is away to modify the dimmer to be the same.
 

·
Registered
Joined
·
2,094 Posts
OK thats not a PWM circuit, well not in the same sense as what slot people call PWM. Do you own a multimeter? Without any power to the cct check to see if the two -ve terminals give essentially zero ohms or a high reading. If its zero ohm reading then the two -ves are common and it should work. If it gives a high resistance reading then the output -ve is floating and youre stuffed.

Why not use a simple 50 ohm 10W wire wound pot? Or something similar?

cheers
rick1776
 

·
Tel
Joined
·
4,031 Posts
Connecting the multimeter to both -ve terminals shows no line.
Erm ... I didnt look for the pot as I didnt know what sort I wanted.
I can now have a look !

Edit: hmm not cheap are they !
 

·
Tel
Joined
·
4,031 Posts
Discussion Starter · #18 ·
How important is the ohm rating ?
I would imagine 5w should be plenty for the motors I use.
 

·
Phil Kalbfell
Joined
·
3,373 Posts
I have a rotary multi position switch with diodes across the terminals so I can vary the voltage to the track in steps of 0.6 Volt with each step.I have this connected to a plug and simply plug it into the controller socket, I use it for " track packing" before race nights, should do just what you want to do.
 

·
Registered
Joined
·
2,094 Posts
You probably want something between 25 to 50 ohms for a scaly type. 50 might be a touch high but that just means the first part of the pot will be dead before the car starts to move. The hotter the motor the less ohms you will need and the more watts.

cheers
rick1776
 
1 - 20 of 21 Posts
Top