Recommendations - Model Train Controller

[Darrel Taylor]

Grreat!

One by one, knocking out the problems.

As for sticking with it, I'll stick with anyone that put's in the effort. Like you.
Thanks for making it fun.

Steve,
Do you hear the whining etc in your motors?
Just wondering if it's the type of motor that makes a difference.
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[mister_e]

Yeah that's what i thought too, hence why i buy few different model.

Well, yes i hear some little noise which is more or less louder depending of the model... but there's always some noise when you play around the minimum low-voltage threshold.

I tried higher PWM frequencies and it may cure some part of the problem on some voltage range and on some motor model. but it's certainly not perfect on ALL motor i have here.

To me, in this specific case, a better choice could be to use some kind of linear regulation. Something around the following.

<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=1396&stc=1&d=117175510 5">

it have some good point and some bad ones. But do you really a 0-100% regulation? mmm

Malc, don't worry... it's an interesting and funny thread.

An idea... we could skip the PWM and use some I2C DAC...

[Acetronics2]

Yeah that's what i thought too, hence why i buy few different model.

Well, yes i hear some little noise which is more or less louder depending of the model... but there's always some noise when you play around the minimum low-voltage threshold.

I tried higher PWM frequencies and it may cure some part of the problem on some voltage range and on some motor model. but it's certainly not perfect on ALL motor i have here.

To me, in this specific case, a better choice could be to use some kind of linear regulation. Something around the following.

<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=1396&stc=1&d=117175510 5">

it have some good point and some bad ones. But do you really a 0-100% regulation? mmm

Malc, don't worry... it's an interesting and funny thread.

An idea... we could skip the PWM and use some I2C DAC...

Hi, Steve

Your design is to try with a low input RC constant in order to produce some kind of trapezoidal wave ... instead of the beautiful square wave.

the problem lays in the slew-rate ... remember lentz's law ... the motor windings oppose an "electrical inertia" proportionnal to the slew-rate ...

that will create some dissipation in the ballast ... but make less noise and heat.

may be some "Mid freq" rectified sinus, used in burst mode could also do the job with minimal issues ( seen on the motor side ... LOL !!! )



Alain

[mister_e]

My motor theory is far far away... and never felt the need to understand it in the past

interesting... thanks.

Few interesting points in the followings ...
http://homepages.which.net/~paul.hil...llersBody.html ok ok it's talking about a starter but anyways..

http://ww1.microchip.com/downloads/e...tes/00770b.pdf

[malc-c]

Guys,

Just thought you might want to see the prototype controler (only two channels)



The 10K pot and reversing switch is connected via the 6-pin header infront of the power transistors. I've also left room for a small heatsink, but in tests so far these don't get hot enough to warrant one !

The only problem is I'm still waiting on some 16F676's as I fried the only one i had in the breadboard... (got distracted by a phone call and connected the +12v to the PIC rather than the +5v !!! - it was glowing and had to cut short the call to pull the plug !!) - Tested the output stage and it works fine so can't see any reason for it not to work when the PIC's arrive.

[mister_e]

The only problem is I'm still waiting on some 16F676's as I fried the only one i had in the breadboard... (got distracted by a phone call and connected the +12v to the PIC rather than the +5v !!

Looks good! Keep us posted!

[malc-c]

Grreat!

One by one, knocking out the problems.

As for sticking with it, I'll stick with anyone that put's in the effort. Like you.
Thanks for making it fun.

Thanks Darrel,

I'm always willing to put effort in to these projects, and I've learnt a lot over the course of this thread. I just feel a tad embarrased that I didn't try two seperate power supplies earlier and kept pointing the finger at the code...

Mind you, hopefully the use of your PWM routines in this application may of hi-lighted some areas such as the armature noise, that you may want to look at for future verions.

As for the motors, I have four 2mm scale locos, two are circa 18 years old with an open frame 5 pole motors, the others are less than a year old and both have small can motors... guess which ones produce the better running... yup the older ones !!

As a side note, when I tried your last bit of code I was using a 4mhz Xtal, I then tried it with a 20mhz and it was quite painful, for my ears and the motor !!

Anyway, thanks once again to you and Steve for all your help. To everyone else who's been reading this, sorry if it bored you at times