Pwm speed controller

[nickf87]

Anybody have any views on using a pwm speed controller 12v dc with reversing switch from China as a control or has anybody done this thanks in advance

[PatB]

Similar items have been discussed before so a search might throw something up. I think the consensus was that it would be worth a try  but that something not designed as a model railway controller may not adjust all the way down to zero.

[DCB]

Worth a try?, with locos so cheap at the moment....   Personally I find PWM noisy and not friendly to motors and would not touch it with a barge pole, but I use a rotary switch and loads of diodes to provide a voltage regulated power supply with 11 steps so my views are very much in a minority.  I suppose you could always put a capacitor across the output with an on off switch to get both PWM starts and smooth running at line speed.

[dhjgreen]

Not as cheap as the chinese PWM controllers, but I have just bought 2 Varipulse controllers from Canada (12v AC needed). There are some reviews on here, not all positive; just search varipulse on here to see them. BTW anyone using DCC is using PWM (at 79 Hz default setting; info courtesy of MERG).

Edited January 20, 2016 by dhjgreen

[Gordon H]

Not as cheap as the chinese PWM controllers, but I have just bought 2 Varipulse controllers from Canada (12v AC needed). There are some reviews on here, not all positive; just search varipulse on here to see them. BTW anyone using DCC is using PWM (at 79 Hz default setting; info courtesy of MERG).

 

I am intrigued as to where you obtained this 79Hz figure. What does it relate to?

While it is certainly true that DCC loco decoders use PWM as a method of driving the motor for reasons of efficiency, the PWM frequencies in use these days are typically into the tens of kilohertz range, so usually above the audible range. In the early days of DCC the processors available for use on decoders were rather limited in their capabilities and speeds, so lower PWM rates were often encountered but that time is long gone.

The PWM rate the motor sees via the decoder bears no relationship to the waveform on the track, which is simply information encoded into raw power.

[dhjgreen]

I am intrigued as to where you obtained this 79Hz figure. What does it relate to?

While it is certainly true that DCC loco decoders use PWM as a method of driving the motor for reasons of efficiency, the PWM frequencies in use these days are typically into the tens of kilohertz range, so usually above the audible range. In the early days of DCC the processors available for use on decoders were rather limited in their capabilities and speeds, so lower PWM rates were often encountered but that time is long gone.

The PWM rate the motor sees via the decoder bears no relationship to the waveform on the track, which is simply information encoded into raw power.

As I said above, the information is from MERG, in their handbook, it gives the recommended rate for various types of motor and gives 79 Hz as the default, giving the CV code values for other frequencies. They do talk about high frequency decoders; maybe the handbook needs updating. We will see if anyone from MERG is looking here.

 

I had intended putting a 'scope on a motor to check for myself, I now will.

 

I am quite well aware of your final comment, thanks anyway.

[dhjgreen]

I have just had a 'scope directly on a motor, I withdraw my 79 Hz statement, it is far more complex than than that; I will contact MERG re an update to the handbook.

[Gordon H]

As I said above, the information is from MERG, in their handbook, it gives the recommended rate for various types of motor and gives 79 Hz as the default, giving the CV code values for other frequencies. They do talk about high frequency decoders; maybe the handbook needs updating. We will see if anyone from MERG is looking here.

 

I am a member, but still unsure what document you are referring to.

What is it a 'handbook' for?

Can you provide a link to where you found it? As you say, it probably needs updating if it is still available.

[dhjgreen]

I now cannot find where I got this information, it it not where I recalled finding it, I therefore withdraw any references to MERG in previous statements.

[kevinlms]

I now cannot find where I got this information, it it not where I recalled finding it, I therefore withdraw any references to MERG in previous statements.

But perhaps you're correct in principle, about early decoders having frequencies in the sort of ranges you mentioned? Now modern DCC decoders use 'Silent Drive' type, which means using a frequency that humans can't hear.

 

This page suggests that 'early decoders (first generation)' used the range between 30Hz to 200Hz.

 

https://sites.google.com/site/markgurries/home/decoders/decoder-motor-tuning/decoder-motor-drive-evolution

[DCB]

Has anyone tried taming a PWM controller by putting a big capacitor across the output?

[Gordon H]

I would guess someone has at some time, but it is not something to encourage without knowing what kind of output stage the particular controller has, what frequency it is running at etc, etc. There is no single definition for PWM controller designs as such, they just employ a time based variation concept rather than direct voltage level.

If it is a simple emitter follower output or similar, i.e. a single ended drive, a big capacitor on its own will likely charge to the full output voltage very quickly, assuming the driver can take the strain, so little or no benefit there.

An H Bridge output (like a DCC decoder has) would likely suffer even more, and would need a bipolar capacitor to be used.

If you want to try anything like this, it needs to be a properly defined filter circuit that you add, set up for the PWM rate being used, and rated for the currents to be encountered.

Could be as simple as an LC, RC or LCR type.

[Grovenor]

 

BTW anyone using DCC is using PWM (at 79 Hz default setting; info courtesy of MERG).

As others have said, this does not ring any bells as MERG advice, it reminds me more of the original ZTC decoder manual. The early ZTC decoders had the PWM frequency adjustable by CV from a minimum of about 40Hz up to 200 or so and then a high frequency for silent drive. The manual gave recommended frequencies for different types of motor. In the absence of feedback control low frequencies could give better slow running.

If this info does appear in a MERG document it probably dates back to those days.

Regards

[dhjgreen]

As others have said, this does not ring any bells as MERG advice, it reminds me more of the original ZTC decoder manual. The early ZTC decoders had the PWM frequency adjustable by CV from a minimum of about 40Hz up to 200 or so and then a high frequency for silent drive. The manual gave recommended frequencies for different types of motor. In the absence of feedback control low frequencies could give better slow running.

If this info does appear in a MERG document it probably dates back to those days.

Regards

I withdrew my MERG statement some posts ago

http://www.rmweb.co.uk/community/index.php?/topic/107317-pwm-speed-controller/?p=2199885

[Gazbo]

I bought a new PWM unit from Ama-zonk yesterday.

(Not yet arrived - fingers crossed !)

digital readout panel at front, with adjustment knob built into the front right hand side

Encoder control, as opposed to a pot.

ie: turn to adjust,

With a short press for on and off.

long press to access menus.

I also intend to post -insert a crossed DPDT, (either on/off/on, or on/on) into the output lines, for the usual directional control.

 

Its programmable for soft start/stop, from zero - up to around 9.9 seconds.

The output max/min endpoints are also settable, which will be handy.

The frequency is adjustable between (I think) - 1 to 100 Khz.

Not completely sure there, because in the pigeon English blurb -it actually states 1kHz - 00kHz, with the factory preset being at 20kHz.

that's the bit I'm unsure of. 

I'm running DC only, predominantly Xo3/Xo4's, which ran fine on my last PWM unit. 

Does anyone have any idea, roughly what kHz I ought to be running in (Ballpark)?

(Can't find a CV9 for these motors.)

I think I read somewhere - it wants to be around 20 to 25. (Before adjustment, Factory default is set at 20kHz)

 

Thanks guys.

Edited July 6, 2022 by Gazbo

[Barclay]

On 04/07/2022 at 19:41, Gazbo said:

I bought a new PWM unit from Ama-zonk yesterday.

(Not yet arrived - fingers crossed !)

digital readout panel at front, with adjustment knob built into the front right hand side

Encoder control, as opposed to a pot.

ie: turn to adjust,

With a short press for on and off.

long press to access menus.

I also intend to post -insert a crossed DPDT, (either on/off/on, or on/on) into the output lines, for the usual directional control.

 

Its programmable for soft start/stop, from zero - up to around 9.9 seconds.

The output max/min endpoints are also settable, which will be handy.

The frequency is adjustable between (I think) - 1 to 100 Khz.

Not completely sure there, because in the pigeon English blurb -it actually states 1kHz - 00kHz, with the factory preset being at 20kHz.

that's the bit I'm unsure of. 

I'm running DC only, predominantly Xo3/Xo4's, which ran fine on my last PWM unit. 

Does anyone have any idea, roughly what kHz I ought to be running in (Ballpark)?

(Can't find a CV9 for these motors.)

I think I read somewhere - it wants to be around 20 to 25. (Before adjustment, Factory default is set at 20kHz)

 

Thanks guys.

Hi I have had one of these for a while and it works very well. I installed it in a box with a DPDT switch for reversing.

 

In terms of the frequency to select, a little experimentation is worth trying. I think somewhere between 10-30 Khz has been recommended elsewhere. I have mine at 15 and it seems fine with all my loco's. Control is good - in many ways smoother than some of my feedback controllers and nearly as good overall as the Pentroller that's still my favourite.

 

 

[DCB]

That is a strange looking Bo Bo to the right of the meter.  It looks like more than one Triang Dock shunter body on a class 20 frame?  Am I right?

 

 

On 18/07/2022 at 12:08, Barclay said:

H

 

 

 

[Barclay]

4 hours ago, DCB said:

That is a strange looking Bo Bo to the right of the meter.  It looks like more than one Triang Dock shunter body on a class 20 frame?  Am I right?

 

 

 

Hi - yes it was a lockdown piece of nonsense but great fun to build. 2 broken dock shunter bodies, some plasticard, spare etched grilles, and simple scratchbuilt bogies with some old Athearn sideframes - whatever fitted went on it !

 

 

 

[spamcan61]

mmm looks interesting, presumably one of these?, if one is brave enough to go direct to China (hardly a major financial risk) :-

https://www.aliexpress.com/item/1005003015601933.html

 

Some rattling about on Amazon from various sellers:-

https://www.amazon.co.uk/diymore-Controller-Adjustable-Regulator-Generator/dp/B09MQP52ZR

 

Edited July 29, 2022 by spamcan61

[Barclay]

I realise mine is a slightly older version, but, yes, it came direct from China. As you say, no risk, except for a few quid perhaps. However these suppliers are generally reliable, and look at the mark-up on the Amazon one !

[ejstubbs]

On 19/01/2016 at 22:41, nickf87 said:

Anybody have any views on using a pwm speed controller 12v dc with reversing switch from China as a control or has anybody done this thanks in advance

 

There was a previous discussion about this very subject last year, sparked by a post from Barclay:

Unfortunately all but one of my waveform photos in that thread succumbed to the Great Hosting Meltdown of 2022.  I think I still have them somewhere so I might be able to put them back on that thread.

 

I think one difference between the ZK-MG that I used, and the ZK-MGP that is mentioned on this thread is that the ZK-MGP has programmable slow start and slow stop times whereas on the ZK-MG the slow start is fixed and the stop is instant.  It's not clear to me what the "step size" setting on the ZK-MGP is for.

Edited July 29, 2022 by ejstubbs

[spamcan61]

48 minutes ago, Barclay said:

I realise mine is a slightly older version, but, yes, it came direct from China. As you say, no risk, except for a few quid perhaps. However these suppliers are generally reliable, and look at the mark-up on the Amazon one !

Then think what Maplin would be charging, probably 50 quid!

[ejstubbs]

Out of interest, I just did a quick check and I can see that I paid £3.78 for my ZK-MG on eBay in April last year.  That was shipping from China.  The three listings for the same item I've found on eBay so far today are in the £12 region, all from UK stock.  I can't find the ZK-MGP on eBay at all.  The Amazon listing for the ZK-MGP is actually cheaper than the eBay listings for the ZK-MG!  I'm tempted to try out the ZK-MGP - it looks like it should be a straight swap-in to the box I made for the ZK-MG.  The choice would therefore appear to be £5.94 and wait a month from AliExpress, or £11.59 and get it next week from Amazon.  Hmm...

 

On 04/07/2022 at 19:41, Gazbo said:

The frequency is adjustable between (I think) - 1 to 100 Khz.

Not completely sure there, because in the pigeon English blurb -it actually states 1kHz - 00kHz, with the factory preset being at 20kHz.

that's the bit I'm unsure of. 

 

I think the typo in that instance is that "00kHz" should be "99kHz": that's the figure that appears everywhere else in both the Amazon listing and the one on AliExpress.  Not that the odd 1kHz is really here or there.