Info req'd on keyfob R/C

[tramcar trev]

I certainly will... the vastly more expensive 3 channel one seemed to be more predictable in its actions BUT further testing when I get home from my tour of the Artesian Basin Hot baths I'll play some more with it. I tried it with 3 x 12V 10watt globes as a load and though the 3 channels could not be independently controlled it ran happily flashing all 3 lights for a day or so... BUT MORE RIGOROUS TESTING IS NEEDED!!!

http://www.ebay.com.au/itm/350687616075?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

 

[ge_rik]

When you've cracked it let me know!

Ditto - Although I have one of the earlier controllers installed in my railbus, it is not 100% reliable. Sometimes it works OK but it is temperamental. I've always assumed it was interference from the track etc but Mick's experiences suggests it might be something more deep-rooted. They seem Ok when controlling LEDs, which is of course what they were designed for, so I have wondered if motor back-emf is mucking up the electronics. I may try adding a couple of capacitors to the motor terminals to see if that improves things.

Rik

 

[tramcar trev]

I installed one to control the LED lighting in my Caravan..... Erratic behavior after a while....

Maybe back emf is the cause as they seem to reset if the power is turned off.... C'mon give us a clue as to type and size of capacitor and I'll try it too...
If I put a large cap across the motor that is going to provide some inertia so stops will be more gradual and starts would be "softer" so a smaller cap would kill off any rf I would assume... But this is beyond me.... Makes sense though.... but someone on the forum would be able to calculate exactly the size of the capacitor needed...

 

[gregh]

Maybe back emf is the cause as they seem to reset if the power is turned off.... C'mon give us a clue as to type and size of capacitor and I'll try it too...
If I put a large cap across the motor that is going to provide some inertia so stops will be more gradual and starts would be "softer" so a smaller cap would kill off any rf I would assume... But this is beyond me.... Makes sense though.... but someone on the forum would be able to calculate exactly the size of the capacitor needed...

I've been suspecting back emf all through this discussion. To stop back emf, you could try some of the options in this sketch - no guarantees! I'm assuming the led controller has a PWM type output.

[style="color: #ff6600;"]IMPORTANT - CIRCUIT GOES BEFORE REVERSING RELAY CONTACTS to keep polarity correct.

Try D1 first - it might 'mimic' the usual feeding into leds. To do the testing, you could use any 1A rated diode, but for a final setup, use something bigger to match the current draw of the motor.
If no help, try D2 as well. It can be 1A rated.
C1 - you can start with 0.1 uF and go up to 4700 uF if you want. Depending on the frequency of the led controller, you will find the max size that still allows you speed control. Too big and it will appear as full on all the time.

There's no way you can use a big capacitor to give a 'soft stop' feature when using PWM type control (as the led controller probably is) The cap just charges up to the peak voltage and the power is full on all the time. It has to be small enough to allow it to completely discharge into the motor during the PWM off time.

I also suspect that when you get to test it with power supplied through the rails and not a battery, the bad contact between rail and wheel may cause problems with the led controller. How have you done your testing so far? battery? solid connection to power supply?

 

[tramcar trev]

Yep, the led dimmers are PWM... And yes I did test it using a power supply where the results were good.... Remember though that it works (well mine does) for a while in use under "real conditions in a tram". When I get back from my tour of the Artesian Basin I'll try out your suggestions from the sketch...
Between my supply and the led dimmer I take off 12V for my lights, I assume that is not going to cause problems.
I have a bag of 3 amp diodes, this gives me a use for them. I also have a bag of rectifiers 2 amp I could put one of those between the dimmer output and the reversing switch, the only reason being that it would stop anything coming back down the line and they are small and easily wired in thus tricking the Dimmer into thinking it was supplying a string of LEDS...
If this works you do realise that you will be probably given the G scale Medal of Honour? and everyone who has thrown out the elcheapo LED dimmers will have to rummage through their junk to get it back...

 

[gregh]

I have a bag of 3 amp diodes, this gives me a use for them. I also have a bag of rectifiers 2 amp I could put one of those between the dimmer output and the reversing switch, the only reason being that it would stop anything coming back down the line and they are small and easily wired in thus tricking the Dimmer into thinking it was supplying a string of LEDS...

I can't see that the tram leds before the led controller would affect it.
Not sure what you mean by 2 amp rectifiers - a bridge with 4 diodes? Using that would just give more voltage drop between the dimmer and motor.
I'd just go with a 3A diode.
Have fun wallowing in the hot artesian water

 

[ge_rik]

When I get back from my tour of the Artesian Basin I'll try out your suggestions from the sketch...

Have fun wallowing in the hot artesian water

Ohh - I see. I'd assumed this was some sort of Aussie euphemism.

If this works you do realise that you will be probably given the G scale Medal of Honour?

Hear! Hear!
.... or at the very least a Boy Scouts 'electronics' badge

Rik

 

[gregh]

Just found this info from Dave Bodnar about using a diode as I suggested for D2. He also has a proposal for reversing.
http://trainelectronics.com/Articles/RadioControl-LED-8Amp/ < Link To http://trainelectronics.c...RadioControl-LED-8Amp/

 

[ge_rik]

Just found this info from Dave Bodnar about using a diode as I suggested for D2. He also has a proposal for reversing.
http://trainelectronics.com/Articles/RadioControl-LED-8Amp/ < Link To http://trainelectronics.c...RadioControl-LED-8Amp/

That's brilliant, Greg - thanks

Just a quick question. Dave says in his article that back-emf will blow the Mosfet. Does that mean that mine is probably already blown and hence is why it's proving unreliable? Or does the fact that it works from time to time suggest the Mosfet is still OK? It's not the expense of replacement that bothers me it's just that where I've mounted the circuit board will mean partial dismantling the model to get at it.

Rik

 

[gregh]

That's brilliant, Greg - thanks
Just a quick question. Dave says in his article that back-emf will blow the Mosfet. Does that mean that mine is probably already blown and hence is why it's proving unreliable? Or does the fact that it works from time to time suggest the Mosfet is still OK? It's not the expense of replacement that bothers me it's just that where I've mounted the circuit board will mean partial dismantling the model to get at it.
Rik

I'd say your mosfet is OK. If it's failed it is either fully on or fully off.
Dave's quite right saying the mosfet can be damaged by back emf. But I think the reason we need the diode is to stop the back emf confusing the dimmer control cct.
Interesting that he seems to have had no control problems with the unit. I wonder if he tried it first without the diode.

 

[Neil Robinson]

My three channel version finally arrived earlier this week, however model railways are rather low priority at the moment so it'll probably be even longer than usual before I get around to much experimentation.
From the instructions I see that patterns 1,2 and 4 are the three primary colours, presumably given by the appropriate single channel output; 3,5 and 6 are the secondary colours and 7 is white.
I'm wondering if connecting the track to red via a reversing relay with the 6V relay coil to blue will give forward travel when red is selected and reverse with magenta (purple in the instructions) as magenta is given by mixing red and blue.
A five or six volt drop given by a series of diodes would be needed in the track wire to allow the relay coil to operate before the loco moves and the blue output would need a 6V voltage regulator.
The diodes may help reduce back emf as mentioned earlier by Greg in post # 91; as for capacitance the unit may replace a blown Train Engineer so I'll nick the capacitors from this. For "linear" output the T.E. has 2000uF across the output, for "PWC" this is switched to be across the controller input.

 

[MRail]

...however model railways are rather low priority at the moment...

WHAT????

 

[tramcar trev]

When I get back from my tour of the Artesian Basin I'll try out your suggestions from the sketch...

Have fun wallowing in the hot artesian water

Ohh - I see. I'd assumed this was some sort of Aussie euphemism.

If this works you do realise that you will be probably given the G scale Medal of Honour?

Hear! Hear!
.... or at the very least a Boy Scouts 'electronics' badge

Rik

Na definitely relaxing in a steaming hot artesian bore.... And for at least 5 minutes after getting out I feel like a new man.... I'm thinking of patenting a sort of wetsuit that is filled with hot mineral water and can be worn all day....

 

[tramcar trev]

...however model railways are rather low priority at the moment...

WHAT????

Yeah C'mon, fair suck of the sav.....

 

[ge_rik]

I'm thinking of patenting a sort of wetsuit that is filled with hot mineral water and can be worn all day....

Funny you should mention that. The last time I wore a wetsuit I found a way ........... (perhaps not!)
Rik

 

[ge_rik]

BTW - just seen this link on the 16mm ngm forum
http://www.trademe.co.nz/toys-models/lego-building-toys/meccano/auction-611496412.htm < Link To http://www.trademe.co.nz/.../auction-611496412.htm

Might be useful for a small model as it seems to be limited to 6v and has no speed control - but does include reverse.

Rik

 

[tramcar trev]

Well unfortunately back from the Artesian basin and I have had a good fiddle with the Keyfob unit on a Bachmann tram. I fitted the "flywheel" diode across the output of the receiver/controller and a 10N capacitor as per Gregh's recommendation and the result is amazing.... works like a bought one, response is good, control is smooth and no untoward noise from the motor. The 10n cap I put across the brushes on the motor and it visibly killed sparking on the commutator.... All is well.... Now as I'm building the Steam tram motor I have to think about a non electrified extension and a name change to the LVS&ET or the LVE&ST, it will mean new uniforms and new brass plaques and new business cards.... It never ends.....

 

[ge_rik]

Well unfortunately back from the Artesian basin and I have had a good fiddle with the Keyfob unit on a Bachmann tram. I fitted the "flywheel" diode across the output of the receiver/controller and a 10N capacitor as per Gregh's recommendation and the result is amazing.... works like a bought one, response is good, control is smooth and no untoward noise from the motor. The 10n cap I put across the brushes on the motor and it visibly killed sparking on the commutator.... All is well.... Now as I'm building the Steam tram motor I have to think about a non electrified extension and a name change to the LVS&ET or the LVE&ST, it will mean new uniforms and new brass plaques and new business cards.... It never ends.....

Sounds great Trev. Can you clarify, what's a 10n capacitor?

Rik

 

[gregh]

Sounds great Trev. Can you clarify, what's a 10n capacitor?
Rik

10n would be 10 nF or 10 nanoFarad. or 0.01uF (1 nF =0.001uF)

My original suggestion was 0.1uF or 100nF. So we'll see whether Trev used 10nF or was having a seniors moment and forgot the extra zero.

Whatever, the result sounds very promising. I MAY even try one for a smaller loco.
I wonder would it be possible to use a 2nd one for reversing, assuming space is OK

 

[tramcar trev]

Sounds great Trev. Can you clarify, what's a 10n capacitor?
Rik

10n would be 10 nF or 10 nanoFarad. or 0.01uF (1 nF =0.001uF)

My original suggestion was 0.1uF or 100nF. So we'll see whether Trev used 10nF or was having a seniors moment and forgot the extra zero.

Whatever, the result sounds very promising. I MAY even try one for a smaller loco.
I wonder would it be possible to use a 2nd one for reversing, assuming space is OK

I have a box of assorted caps but they are all too large capacity so I bought some from Jaycar RC5348 10N so it would be 0.01nF.... Not at all certain that it's necessary but as I said it kills the commutator sparking so that's good for life of the commutator I suspect.

A novel idea Greg, yes you could use 2, they are as we have discussed individually coded but maybe you would need diodes to protect them from the reverse voltage probably... one for forward the other for reverse....
I'll have a play with the 3 channel one, it can be set up so that channel one can be controlled for speed while channel 2 & 3 do a cyclic on/off thing - I'm thinking connect the smoker up to another channel for effects...