Large Scale Central

Zimo MX695KN smoke chuffing

Electronics DCC
#21

Thanks, Dan.

I set up and external MOSFET and optoisolator to power the heater directly from the battery, and everything is working now.

I’m curious why the supplies for the heater and lights would need to be separated. I assume the low voltage outputs are just regulated versions of the V+ terminal? Since I’m using CL2N3s, the supply voltage is irrelevant for my lights.

18V at 100% duty cycle did prove to be too much for the smoke unit, though. Moments after I took this video, it burst into flames. I’ll have to reduce the duty cycle.

#22

HAH!

With pretty high fan speed, my all metal USAT units could tolerate 9v continuously and drew about 1 amp, and the plastic units like Zimo, Aristo, etc, in my opinion, can’t handle this much. I think you were basically at double that in a plastic unit.

I would guess that you want to measure the average power into the unit, since you have PWM and keep it to about 9 or 10 watts, and that would only be with the fan going pretty much full out most of the time. I’d get an analog meter to see if you can get a reasonable average reading of the current.

If not, another way would be to get a cheap thermal IR “gun” and read the temp and make sure you have a situation where the temp equalizes (and below the melting point of the plastic ha ha)

No video of the flames? You are no fun! (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)

Greg

#23

We had one of the club layouts set up today, and I had really wanted to run the Hudson with smoke. On the way out the door, I grabbed the soldering iron and some tools. I grabbed some wick from Home Depot in the tiki torch department, and stopped at the electronic surplus place to get some resistors to smash for heat elements. I performed surgery on a folding table, and got her up and running.

The resistor that came with the unit was 14 ohms. I switched to 18 ohms, and the unit ran for hours without burning up.

#24

Trainli had 2 different prosmoke units.

Older ones that looked like Aristo could run from 10 volts on the heater element, but the newer version needs 15 volts!!

To control the heater, CV 137, 138, 139 need adjustment but one has to make sure the function key for smoke has CV114 set to ignore light dimming if cv 60 is not 0.

#25

I haven’t changed CV60. I did setup 137, 138, and 139. Everything is working great. Two oddities, though:

  1. CV139 is set to 0, but the smoke unit doesn’t fully shut off at idle.

  2. The function controlling the smoke turns off the heater, but the fan keeps pulsing when it’s off.

neither if these is is really a problem, just odd.

#26

What function key is used for the smoke? If function 6 then cv 132 must be set to 72.to get cv137-139 to operate correctly…

#27

Function 8. CV 160 is set to 72. It’s working - F8 turns the smoke on and off, and the PWM duty cycle does change between acceleration, constant speed, and idle. It just doesn’t fully turn off at idle.

#28

Eric, if you ever get a chance in the future, it would be interesting to see what current you are running.

Have you measured the decoder to see what it has rectified the track voltage to? Also interested… my guess is that you are a bit under 1 amp at full chat on the heater.

Greg

#29

Eric Reuter said:

I haven’t changed CV60. I did setup 137, 138, and 139. Everything is working great. Two oddities, though:

  1. CV139 is set to 0, but the smoke unit doesn’t fully shut off at idle.

  2. The function controlling the smoke turns off the heater, but the fan keeps pulsing when it’s off.

neither if these is is really a problem, just odd.

Isn’t 139 the acceleration one? The idle setting is CV 137 right?

Greg

#30

The heater is drawing 0.9 A and change. 18.1 V into 18 Ohms. The rectified voltage is just under 18 V. I forget exactly. However, I’m no longer running the heater through the decoder. It’s tied to the battery with a P-channel MOSFET inline. This is driven by an optocoupler that is attached to the decoder.

Yes, I had the CVs backwards in my post, but not in real life. Plenty of smoke during accel. Good catch.

#31

Just checking, trying to update my page on Zimo tips for smoke… part way down, you and Dan are credited

(not finished yet)

https://elmassian.com/index.php?option=com_content&view=article&id=652:zimo-decoder-tips&catid=55&Itemid=902

As soon as I dig into my Hudson, I’ll try some fun with an MTH or USAT unit.

So do you basically just have on and off on the heater?

Greg

#32

Greg Elmassian said:

So do you basically just have on and off on the heater?

No, it’s PWM. The function output modulates the opto and that modulates the gate of the FET. I feel like this is a cleaner way to drive the heater, since it avoids running all that current through the Convrtr and decoder. Obviously more work, though. Here’s a schematic.

One thing that I discovered is that the chassis in the Hudson ends up getting grounded through the motor, and that ground, of course, is the virtual ground of the DCC decoder, NOT battery ground. This should probably be noted somewhere, as anything pre-CONVRTR needs to be kept away from the chassis.