Multimeter discrepancy

[melmerby]

1 hour ago, WIMorrison said:

 The comparison between the different waveforms will be very interesting and may be reflective of the different makes.

Here are the two waveforms.

First Lenz:

 

Then Z21:

 

Little to Choose IMHO

For the record I tried the Lenz without load and with a 1A resistive load and there was imperceptible difference between them.

The Z21 is off load.

[melmerby]

For comparison I've just done another capture using the Z21 across the running rails in the middle of the layout, this time it was active:

 

 

 

 

[SHMD]

2 hours ago, melmerby said:

It's a Picoscope (UK designed and made) which is powered from a USB port on a computer.

https://www.picotech.com/products/oscilloscope

 

The software is as supplied and comes with a lot of serial decoding options

It has been updated several times which has added functions.

All scope units also include a useful function generator.

Prices start at around £100 inc VAT for the cheapest single channel 10Mhz device

The one I have is a 2205A which is a two channel 25MHz device.

 

You can buy direct from PIco or from Farnell, Amazon etc.

 

 

Thanks Melmerby, that is really useful.

I have an old Pico Scope but that used the parallel port and I cant remember the last time I used it (2003?).

 

I have an account with two out of three of the venders you quoted. I'll have a look at them in Farnell (great support if out goes wrong + %10 off at the mo)

 

 

Thanks again,

Kev.

 

[melmerby]

Just been back to the days of the AVO and fished mine out of the shed.

Apart from the glass having fallen in and the SP2 (yes, remember them?) battery for Ohms measurements having turned to goodness knows what it worked fine.

Re-fitted glass cleaned some of the grot out of the battery compartment and hey presto, it measures DCC to within about half a volt!

I also found out it was an AVO 9 MkIV (unless someones changed the movement!), I always thought it was an AVO 8!

 

So go to a car boot and pick up a cheap AVO. Good enough and better than the cheapo DMMs

[TheQ]

16 minutes ago, melmerby said:

Just been back to the days of the AVO and fished mine out of the shed.

Apart from the glass having fallen in and the SP2 (yes, remember them?) battery for Ohms measurements having turned to goodness knows what it worked fine.

Re-fitted glass cleaned some of the grot out of the battery compartment and hey presto, it measures DCC to within about half a volt!

I also found out it was an AVO 9 MkIV (unless someones changed the movement!), I always thought it was an AVO 8!

 

So go to a car boot and pick up a cheap AVO. Good enough and better than the cheapo DMMs

Not seen one or I'd have picked it up,  that's where I got my scope.. 

[melmerby]

Just now, TheQ said:

Not seen one or I'd have picked it up,  that's where I got my scope.. 

My Picoscope replaced my earlier (free as scrap) Tek 7704A complete with several plug-ins.

Unfortunately all those plug in components and multiple switches were starting to show the effects of tarnishing and became very unreliable.

So it went to the tip last year.

[Dagworth]

On 28/06/2020 at 18:10, melmerby said:

Here are the two waveforms.

First Lenz:

 

Then Z21:

 

Little to Choose IMHO

For the record I tried the Lenz without load and with a 1A resistive load and there was imperceptible difference between them.

The Z21 is off load.

All of which look a LOT cleaner than the Hornby Select waveform shown on Picotech's website! https://www.picotech.com/library/oscilloscopes/digital-command-control-dcc-protocol-decoding

 

That it also decodes DMX means I have two justifications to buy one, thanks for bringing it to my attention.

 

Andi

[melmerby]

16 minutes ago, Dagworth said:

All of which look a LOT cleaner than the Hornby Select waveform shown on Picotech's website! https://www.picotech.com/library/oscilloscopes/digital-command-control-dcc-protocol-decoding

 

That it also decodes DMX means I have two justifications to buy one, thanks for bringing it to my attention.

 

Andi

Does the select actually meet the NMRA DCC spec? The Elite does but I seem to remember reading the Select didn't

As you can see from the extra waveform I posted with the Z21s waveform at the rails, with 20 + locos on the layout, had lost most of what was already minimal overshoot.

 

I had done these tests before with the DR5000 against the Lenz 100 system and The Lenz was rock solid frequency wise but the DR 5000 had some jitter and a little more (but not a great amount of) overshoot.

 

DMX. Is that for controlling stage equipment?

I seem to recall there is an interface available for DCC so that you can control DCC layout lighting effects.

[Dagworth]

13 minutes ago, melmerby said:

DMX. Is that for controlling stage equipment?

I seem to recall there is an interface available for DCC so that you can control DCC layout lighting effects.

Yes, I work as a lighting engineer (  some work would be nice, gigs would be nice, can't see any happening this year), part of my work is maintenance for one of my local companies. 

 

I'd be very interested to see a DMX-DCC interface!

 

Andi

[Graham Radish]

56 minutes ago, melmerby said:

Does the select actually meet the NMRA DCC spec? The Elite does but I seem to remember reading the Select didn't

As you can see from the extra waveform I posted with the Z21s waveform at the rails, with 20 + locos on the layout, had lost most of what was already minimal overshoot.

 

I had done these tests before with the DR5000 against the Lenz 100 system and The Lenz was rock solid frequency wise but the DR 5000 had some jitter and a little more (but not a great amount of) overshoot.

 

DMX. Is that for controlling stage equipment?

I seem to recall there is an interface available for DCC so that you can control DCC layout lighting effects.

The digikeijs ecosystem to me is absolutely incredible, so many connection options in such a small box, the only bad thing I can say about it is the stock software, its very buggy, I should imagine the next firmware should sort the wifi issues out. if using N gauge the 3.25amp amps it provides is enough for about 14 sound locos probably more.

[WIMorrison]

@Graham Radish don't hold your breath whilst waiting for an update to fix all the issues in the DR5000 software

[Graham Radish]

28 minutes ago, WIMorrison said:

@Graham Radish don't hold your breath whilst waiting for an update to fix all the issues in the DR5000 software

Its come a long way since release but there are still a couple of wifi issues although i rarely use the wifi funtionality itself, the infrared functions are more appealing to me i have a spare logitech 650 universal remote control once i figure out how to use it and what the codes are will be great as it has a colour lcd. ill use it to control the layouts lighting.

 

 

 

 

[Crosland]

12 hours ago, Dagworth said:

I'd be very interested to see a DMX-DCC interface!

 

I have thought of a DCC-DMX accessory decoder for controlling layout lighting rigs but I think DMX is closed source and I was too tight to buy the spec  There's also DALI which has hardware support in some PICs.

 

I would like to see those waveforms zoomed in a bit, and/or sampled at a faster rate, hence my earlier comment.

[melmerby]

13 hours ago, Dagworth said:

 

 

I'd be very interested to see a DMX-DCC interface!

 

Andi

https://www.opendcc.de/elektronik/opendecoder/opendecoder_sw_dmx_e.html

[melmerby]

11 hours ago, Graham Radish said:

Its come a long way since release but there are still a couple of wifi issues although i rarely use the wifi funtionality itself, the infrared functions are more appealing to me i have a spare logitech 650 universal remote control once i figure out how to use it and what the codes are will be great as it has a colour lcd. ill use it to control the layouts lighting.

 

 

 

 

It is IMHO still far from perfect

The problem with it is it seems to be always a work in progress, I have come from around ver 1.1.1 (?) to ver 1.5.5. I now use it only for testing (Arduino DCC projects at the mo)

The Layout is Z21 & Lenz controlled, both rock solid bits of kit.

 

If you want to know what are the codes from the URC build an Arduino IR receiver, will only cost a few pounds and will decode all the buttons.

(then you could use that to control the lighting..........)

[newbryford]

14 hours ago, Dagworth said:

All of which look a LOT cleaner than the Hornby Select waveform shown on Picotech's website! https://www.picotech.com/library/oscilloscopes/digital-command-control-dcc-protocol-decoding

 

That it also decodes DMX means I have two justifications to buy one, thanks for bringing it to my attention.

 

Andi

 

Loving the spikes on the Hornby waveform...…..

 

That'll not be good for the longevity of decoders.

[spamcan61]

3 hours ago, newbryford said:

 

Loving the spikes on the Hornby waveform...…..

 

That'll not be good for the longevity of decoders.

I recall this being discussed back when the Select was released, being a Duette guy* I didn't take too much notice but no, >60V pk-pk doesn't seem nice from a decoder perspective. Mind you I don't know what load impedance DCC controllers are designed for, I would think various different shapes / sizes of train set would present quite different impedances to the controller output circuit.

 

*although I run half a dozen DCC fitted locos now so I figure a nice flat dc o/p voltage controller would be kinder to them than the Duette's output...

Edited June 30, 2020 by spamcan61

[SHMD]

On 28/06/2020 at 16:14, melmerby said:

It's a Picoscope (UK designed and made) which is powered from a USB port on a computer.

https://www.picotech.com/products/oscilloscope

 

The software is as supplied and comes with a lot of serial decoding options

It has been updated several times which has added functions.

All scope units also include a useful function generator.

Prices start at around £100 inc VAT for the cheapest single channel 10Mhz device

The one I have is a 2205A which is a two channel 25MHz device.

 

You can buy direct from PIco or from Farnell, Amazon etc.

 

 

Thanks so much for this information.

My Pico 2000series scope has just arrived from Farnell.

 

What a Joy to use. So intuitive and I already think the Serial Decoding feature is indispensable!

I use RS232, SPI, I2C and DCC, in my PIC projects, so this device is going to get some serious usage.

 

The PicoScope is so portable too, just the jobbie for when I start travelling again.

 

 

Kev

[Graham Radish]

Im not surprised at all about the Hornby spiking, after all primarily they are a toymaker, as far as their locos go i think even the older lima had more accurate bodyshells

Edited June 30, 2020 by Graham Radish

[Graham Radish]

9 hours ago, melmerby said:

It is IMHO still far from perfect

The problem with it is it seems to be always a work in progress, I have come from around ver 1.1.1 (?) to ver 1.5.5. I now use it only for testing (Arduino DCC projects at the mo)

The Layout is Z21 & Lenz controlled, both rock solid bits of kit.

 

If you want to know what are the codes from the URC build an Arduino IR receiver, will only cost a few pounds and will decode all the buttons.

(then you could use that to control the lighting..........)

I should hope so both the z21 and lenz systems are over 3 times the price of the dr5000, the digikeijs system holds it own against them both tbh.

[WIMorrison]

I suggest that you are looking at the wrong place to buy the Z21 or a Lenz system, and if you are willing to accept the issues, problems and unreliable performance then you are a happy man - me? I would rather pay for the quality, stability and reliability, after all even if you paid top price then that would only equate to the cost of one loco. 

[Graham Radish]

2 hours ago, WIMorrison said:

I suggest that you are looking at the wrong place to buy the Z21 or a Lenz system, and if you are willing to accept the issues, problems and unreliable performance then you are a happy man - me? I would rather pay for the quality, stability and reliability, after all even if you paid top price then that would only equate to the cost of one loco. 

The z21 and lenz have problems too, just different problems, only issue ive ever had on my dr5000 is an issue with the wifi app, never had any issues with the unit itself, its been rock solid, i cant justify paying an extra £250 for something that does the same thing. where did you get the unreliable performance idea from? this has been the best system ive ever owned and its £60 less than a Hornby elite (which is a toy)

Edited June 30, 2020 by Graham Radish

[melmerby]

47 minutes ago, Graham Radish said:

The z21 and lenz have problems too, just different problems, only issue ive ever had on my dr5000 is an issue with the wifi app, never had any issues with the unit itself, its been rock solid, i cant justify paying an extra £250 for something that does the same thing. where did you get the unreliable performance idea from? this has been the best system ive ever owned and its £60 less than a Hornby elite (which is a toy)

What problems?

The Lenz 100 has been around years and only recently retired and had an enviable reputation for quality and reliabilty.

The original Lenz USB adapter could be a bit problematical, possibly due to the FTDI VCP chip used but the later LAN/USB one with a different maker's VCP chip was a solid reliable performer.

 

DR5000 problems? Several people with the same issues, will that do? I've had two and they both exhibited the same problem and Iain has also had exactly the same problem.

(BTW the WiFi worked fine when I used it!)

IMHO The DR5000 is a Jack of all trades, master of none.

When it first came out with all it's advertised bells and whistles, the user found certain things hadn't yet been implemented and you needed to keep updating the firmware as extra features were added.

 

Price? DR5000 = £150, Z21 = less than £300, the price difference of one loco.

Hornby Elite? Why would anyone buy one?

[Graham Radish]

Yes but all electronics (especially computer interface based) have problems, thats the nature of software, but the dr5000 unit itself is bloody brilliant, most of the time people are just trying to justify their expensive purchases after all the more expensive the better right? lol it don't work that way, if you browse this site you will see  all problems people are having with the z21AND the lenz systems, they are not immune no matter the price

 

the dr5000 is a wonderful little unit with a lot of useful protocols, as for ease of use its the best ive ever come across.

48 minutes ago, melmerby said:

 

Hornby Elite? Why would anyone buy one?

 

I was making a valid point in the dr5000 being £60 cheaper than a toy. as i said, more expensive is always better yea>? at least digikeijs are still supporting end users with firmware updates.

 

when people look down at you for having cheaper equipment thats pretty lame.

 

 

Edited June 30, 2020 by Graham Radish

[melmerby]

9 hours ago, Graham Radish said:

 

when people look down at you for having cheaper equipment thats pretty lame.

 

 

Who's looking down on you for having cheaper equipment?

I bought a DR5000 because it looked the dogs doolies but how wrong I was.

 

The problem with the DR5000 is not the price but the fact that it was launched too early, with the firmware only partially working.

 

9 hours ago, Graham Radish said:

at least digikeijs are still supporting end users with firmware updates.

 

 

The firmware wasn't fully developed and has had to be revised multiple times to implement the original shortcomings. Fact.

Would you release a new car if the headlights didn't work, the operation of which was to be implemented in a later firmware update?

 

I already had a Lenz system but bought a DR5000 in 2016, shortly after they were released, (it had a very low serial number and was on firmware 1.1.1 IIRC or similar) as a replacement, as I thought the extra functions & connectivity would be useful as my layout developed.

I did run my layout entirely with it for a while (fortuitously I kept the Lenz system) but it exhibited a few flaws including a tendency to "freeze" when being controlled by a computer. It wouldn't respond to changes in throttle or turnout settings, leaving trains dangerously out of control.

 

I updated the firmware numerous times until I was on around ver 1.4.8 (I think) and then decided it was probably faulty as none of these updates had cured the problem. (it was by now long out of warranty)

I then purchased another DR5000 (now including adjustable PSU) assuming the new one wouldn't exhibit the freezing effect. Wrong, it was exactly the same, the firmware was by now up to 1.5.2.

I then learnt that I wasn't the only one that had the same problem and it would appear to be a (so far) incurable inherent fault.

I gave two DR5000s the opportunity to do the the job but they let me down.

 

So I have paid approaching £300 for two DR5000s, the same as one Z21 which does 90% of a DR5000 but is flawless in operation.

The big omission on the Z21 is an RS bus, so my once redundant Lenz 100 system is back in use detecting RS bus activity.