PWM controller

Post all your model railway electronic problems, solutions and discoverys here.
User avatar
Montfort
Posts: 323
Joined: Sun Aug 12, 2018 11:13 am

PWM controller

Postby Montfort » Fri Sep 28, 2018 4:29 pm

Hello everyone,
I am looking for a good PWM controller but I am a little lost. What is the best choice for this type of controller?
Thank you for your help.
Back on the track !
Chris

User avatar
Mountain
Posts: 4305
Joined: Mon Oct 24, 2016 3:43 pm
Location: Somewhere in Wales, UK.

Re: PWM controller

Postby Mountain » Fri Sep 28, 2018 7:52 pm

Out of interest, is PWM the same as feedback or are they different? I certainly know that Gaugemaster do some nice feedback controllers. I used to have the handheld one and it worked greatly.

abenn
Posts: 237
Joined: Thu Jun 05, 2008 11:03 am

Re: PWM controller

Postby abenn » Fri Sep 28, 2018 8:38 pm

I think it would help if you say what you want a PWM controller for :)

I use PICAXE chips to generate PWM to operate servos which control the points on my layout. Is that the kind of thing you're looking for?

User avatar
Flashbang
Posts: 3571
Joined: Thu Oct 18, 2007 1:07 pm
Location: SE United Kingdom
Contact:

Re: PWM controller

Postby Flashbang » Fri Sep 28, 2018 10:44 pm

Montfort wrote:Hello everyone,
I am looking for a good PWM controller but I am a little lost. What is the best choice for this type of controller?
Thank you for your help.

As I posted on the Model Railway Forum to your question....
You need to understand the difference between the two...

PWM (Pulse Width Modulation) is the use of pulses of power at full voltage, the pulses duration is set by the controller speed setting. The amount of full volts available is governed by the pulse to time ratio. Example.. PWM at half power/speed setting is full power at half the time. So full power is provided to the rails and motor but for only 50% of the time. Go to a quarter full speed full power is provided for 25% of the time and is Off 75% of the time. All this is by the On to Off time periods. Half speed is roughly equal On to Off time period, while a quarter speed is approx a quarter On to three quarters Off in the time period. All this is happening at a very fast rate- typically often around 20KHz (20000 times a second) or faster!

Feedback
looks at the back emf (generated back electro motive force from the motor working as a generator between On pulses) of the locos motor and rapidly it adjusts up or down the output voltage to the rails to try and maintain a constant speed. Of course there is a limit to the Bemf that can be read and effectively outputted as rail volts, going down hill is an example where feedback is unable to slow the loco beyond the maximum setting of the speed knob. However up hill or along straights the feedback will try to maintain constant speed up to the controllers setting. Consider this to be similar to a cars cruise control

Gaugemaster offer perhaps the best DC PWM controllers closely followed by Morley.
[Image << Click the Icon to go to my website
Broken? It was working correctly when I left it.

User avatar
Ironduke
Posts: 993
Joined: Mon Sep 26, 2005 12:04 am
Location: Ballarat Victoria Australia
Contact:

Re: PWM controller

Postby Ironduke » Fri Sep 28, 2018 11:02 pm

There are a few simple circuit diagrams around if you fancy making your own. There used to be a range of kits available but I suspect that the rise of DCC has made them fairly obsolete.
e.g.
from
http://www.talkingelectronics.com/EMR-2 ... rottle.pdf
to
https://www.altronics.com.au/p/k6015-ra ... -mkiv-kit/
http://www.siliconchip.com.au/Issue/200 ... s=nonflash
Regards
Rob

User avatar
Montfort
Posts: 323
Joined: Sun Aug 12, 2018 11:13 am

Re: PWM controller

Postby Montfort » Sat Sep 29, 2018 9:19 am

abenn wrote:I think it would help if you say what you want a PWM controller for

My mistake. I want to run at a very low speed my green rocket.
Thank you very much for all your replies.
Back on the track !
Chris

User avatar
Mountain
Posts: 4305
Joined: Mon Oct 24, 2016 3:43 pm
Location: Somewhere in Wales, UK.

Re: PWM controller

Postby Mountain » Sat Sep 29, 2018 11:57 am

Just attach a little parachute. :lol:

User avatar
Montfort
Posts: 323
Joined: Sun Aug 12, 2018 11:13 am

Re: PWM controller

Postby Montfort » Sat Sep 29, 2018 1:33 pm

:lol: :lol: :lol:
Back on the track !
Chris

User avatar
Montfort
Posts: 323
Joined: Sun Aug 12, 2018 11:13 am

Re: PWM controller

Postby Montfort » Sat Sep 29, 2018 4:41 pm

Mountain wrote:Just attach a little parachute. :lol:
Done ! :lol:

SL 29.jpg
Back on the track !
Chris

User avatar
Montfort
Posts: 323
Joined: Sun Aug 12, 2018 11:13 am

Re: PWM controller

Postby Montfort » Sat Sep 29, 2018 4:57 pm

Back on the track !
Chris

User avatar
Mountain
Posts: 4305
Joined: Mon Oct 24, 2016 3:43 pm
Location: Somewhere in Wales, UK.

Re: PWM controller

Postby Mountain » Sat Sep 29, 2018 5:48 pm

They look good. The only thing I would say is to use a form of short circuit protection with them. The second one has a fuse and who wants to keep changing fuses? Use a car bulb if you can't find anything else.

User avatar
Ironduke
Posts: 993
Joined: Mon Sep 26, 2005 12:04 am
Location: Ballarat Victoria Australia
Contact:

Re: PWM controller

Postby Ironduke » Sat Sep 29, 2018 11:26 pm



edit sorry didn't see the screw terminals in the first photo.
Regards
Rob

User avatar
Montfort
Posts: 323
Joined: Sun Aug 12, 2018 11:13 am

Re: PWM controller

Postby Montfort » Sun Sep 30, 2018 11:23 am

Hope that helps...

900.jpg


901.jpg
Back on the track !
Chris

User avatar
Ironduke
Posts: 993
Joined: Mon Sep 26, 2005 12:04 am
Location: Ballarat Victoria Australia
Contact:

Re: PWM controller

Postby Ironduke » Sun Sep 30, 2018 11:04 pm

Yep I saw that later.
Re the fuse: This device is made to drive DC motors at adjustable speeds but it isn't necessarily designed to be regularly shorted out, which is almost inevitable on most model railways. Depends what you're using for a power supply.
What are you going to do for an enclosure?
Regards
Rob

User avatar
Montfort
Posts: 323
Joined: Sun Aug 12, 2018 11:13 am

Re: PWM controller

Postby Montfort » Thu Oct 04, 2018 11:19 am

Ironduke wrote:Re the fuse: This device is made to drive DC motors at adjustable speeds but it isn't necessarily designed to be regularly shorted out, which is almost inevitable on most model railways.
I'll use a car buld as a fuse.
Ironduke wrote:Depends what you're using for a power supply.
I have a lot of transformers with a bridge rectifier.
Ironduke wrote:What are you going to do for an enclosure?
I have a few plastic electrical boxes in stock.
Back on the track !
Chris


Return to “Electronics”

Who is online

Users browsing this forum: No registered users and 8 guests