HM7000-21TXS doesn't work with DCC decoder test board

[LTSR_NSE]

Until someone with the board uses DuPont leads to prove that every pin/track is ok (or not!) or a faulty component is actually identified - speculation about which components might be faulty seems fairly meaningless!

Edited August 15 by LTSR_NSE

[sir john]

As I said previously my esu has a coreless motor I've had no problems setting hm7000 decoders

Edited August 15 by sir john
Typo

[96RAF]

Most decoders use the motor to send an ACK back to the controller to say the command has been received and it can be actioned. A coreless motor may not send back an ACK. More likely it is a physical fault on the board - as Colin says there is precious little component wise to create such an error.

[ColinB]

4 minutes ago, ntpntpntp said:

They draw noticeably less in my experience. That's easily demonstrable just run a coreless motored loco on a bench supply with voltage and current metering, and compare with a similar loco or having an iron cored motor.  When I'm servicing my N gauge locos I expect a typical motor current draw of cored motors to be somewhere around 150mA (quite a bit more when it comes to old 1970s/80s motors), but with locos I know to have coreless motors I see more like 50-75mA.   People upgrading locos with one of the many coreless motor kits out there are noticing the reduction in current draw as well as the improvement in smoothness of running.


Anyway, I'm with @96RAF and this could be a board fault.  It would be interesting to swap the motor for a cored type - or for someone else to connect a coreless motor to their ESU or Lais test board and try a similar test with a HM decoder. 

They draw more, I have just read two articles on them. The reason you use high frequency pwm is that the impedance of coil has an effect and reduces the current. Generally the PWM has to be in excess of 20 kHz according to the article, at DC they look like a virtual short circuit. I don't know what PWM the HM7000 uses, it all depends whether the micro they use has a built in PWM generator or they are doing it by software. With bit bashing (doing it by software) as we used to call it there is no way you can get 20 kHz, but with a PWM module it uses the micros clock pulses to do it. Either way at start up it will look like a short, so it depends how good the overcurrent software is. It could be a board fault but I doubt it, I am assuming the person that posted the original post uses it to test his other decoders so he would have noticed. We already know from other posts that HM7000 has a slight issue with random over currents falsely turning it off.

[96RAF]

12 hours ago, ntpntpntp said:

It would be interesting to swap the motor for a cored type - or for someone else to connect a coreless motor to their ESU or Lais test board and try a similar test with a HM decoder. 

The latest ESU board as Sir John confirms already has a coreless motor and works. All my ESU boards have regular motors.

I am not sure why coreless motors would be specified for model locos as they are designed to run at fairly constant high revs without the need for very fine speed control e.g. in drones and model aircraft. Model railways require good slow running characteristics, with plenty of torque and fine motor control.

[ColinB]

2 hours ago, 96RAF said:

The latest ESU board as Sir John confirms already has a coreless motor and works. All my ESU boards have regular motors.

I am not sure why coreless motors would be specified for model locos as they are designed to run at fairly constant high revs without the need for very fine speed control e.g. in drones and model aircraft. Model railways require good slow running characteristics, with plenty of torque and fine motor control.

I think it is because they give higher torque and are smaller. I think Bachmann use them a lot in their smaller locos. Having read about them I don't know how they work properly on DC but perhaps they rely on them being PWM DC.

[ntpntpntp]

3 hours ago, 96RAF said:

I am not sure why coreless motors would be specified for model locos as they ... require good slow running characteristics, with plenty of torque and fine motor control.

I think the smooth running characteristics without "cogging" was one of the reasons they became popular, along with lower current draw.    Back in the 80s and 90s I used to read about the finescale EM and P4 modellers preferring Portescap, Maxxon, Faulhaber motors for their kit and scratch built locos, with suitable gearboxes to deal with the higher speed and lower torque.

[Rallymatt]

On HM 7000 decoder and coreless motor compatibility, I know of both working together with no issues on a few locos now. 

I am in the process of running some different motor options due to the short lifespan (30-35hrs) of the 3pole variety in the early TT:120 locos and testing some coreless motors is the next phase. These locos are all HM 7000 decoder fitted.
I already have a coreless motor installed in a Roco BR108 but that is running an ESU decoder, heavy shunter that is mainly on dock duty, seems fine.

[ColinB]

Just because it works with an individual's loco it doesn't mean that there isn't an issue, it happens a lot with electronics. I had a TTS in a Duchess after a couple of loops of my layout it would lose sound. Took it out of that loco put it into another and it worked perfectly. Put a Zimo sound decoder in the original loco and it worked without issue. As with all things in engineering it depends a lot on tolerance stack up, it is just with electronics you can't see it. That motor might just have a slight difference in its start up current which causes the issue., who knows? The guy that posted the original concern hasn't come back so he has either given up, or did as I did fitted in his loco and ignored his tester.

[Rallymatt]

My understanding of comments made was, ‘Do coreless motors work with HM 7000 decoders?’ With the obvious caveat, providing the coreless motor is serviceable, the answer is yes they do. 

[Fishmanoz]

Colin, by taking it out of one loco and installing it in another, you are pretty much following the standard troubleshooting sequence (apart from shutting down the app too).  It may well have worked in the first loco after that.

Or maybe you checked?

[ColinB]

2 hours ago, Fishmanoz said:

Colin, by taking it out of one loco and installing it in another, you are pretty much following the standard troubleshooting sequence (apart from shutting down the app too).  It may well have worked in the first loco after that.

Or maybe you checked?

Firstly it was TTS and yes it got taken in and out several times trying to find what the issue was. The loco was brand new so I wasn't about to change motors and Hornby would do what I did, check it worked on DC and class it as no fault found. I tried lots of things, filters on the motor but in the end I just used a different make. So far all the HM7000s have been ok except for the one that just died, but that got replaced. There again I have only used them on Hornby locos virtually all A3 and A4s. There is one fitted to a Dapol class 73 but that is a pretty standard motor.

[ColinB]

4 hours ago, Rallymatt said:

My understanding of comments made was, ‘Do coreless motors work with HM 7000 decoders?’ With the obvious caveat, providing the coreless motor is serviceable, the answer is yes they do. 

I didn't say they didn't Sir John proved that, he said he had no issues. What I am saying is with some it doesn't. As I said we have no communication from the user, so we don't have anymore information. Microprocessors which the decoder contains are very complex beasts sometimes that don't power up as we quite expect them to, sometimes in the "start up" code if you don't enable the interrupts and their masks in the right order you get some funny effects, so it could be a lot of things. Either way we don't know and I doubt there are many on this site do either. I used to write the "start up" code for many of my former employers modules so I learnt a lot, a lot of it the hard way.

Edited August 16 by ColinB