Z scale throttle (fm: F7 retooling)

Jim,
Interesting information. As I said previously, I'm interested in characterizing my snail controller next week because you've brought up some points. Generally, a power supply is measured under load, so an 8V under load from 9.1V is not surprising.
I'm not surprised that the unit will take a higher than 9V input voltage, but I suspect that a higher input voltage does not result in a higher output voltage. Most voltage regulators I've used (and I don't know what is used in the Snail) are designed to output a specific range of voltage independent of the input. Of course, I'll know more once I sit down and play with my unit.

Mark

The no load voltage drop across the Snail is 0.55; with these applied voltages: 9.1 (8.55), 10.0, & 11.5.

Under load of F7 (or GP35) w/9.1 the voltage at my track is 8; when running more load there is more voltage drop -- I^2*R.

Endre Medveczky told me that it will work w/max input of 16V & load of up to 1.5amps.

I suspect the Snail is much like a speed control used in planes, cars, & boats -- they too are PWM.

Those speed controls can operate with various voltages and the output varies up to the supply less the devices voltage drop.

Am a bit disappointed as it does function as I expected -- like "transistor" throttle. Where the trains speed would remain constant -- up or down hill.

From a while ago; I actually considered using the a couple of ESCs.

Resistor:


Simple Transistor:


Airplane PWM Speed Control via Servo Tester

Jim,
I may have missed it in your various posts, but I'm afraid I don't see what your goal is with all this work. Maybe you could describe what you want to do.
In the past, I've built throttles out of the LM317 (easy to find) and the uA723 (long obsolete) voltage regulators. These were pure DC throttles.
Regarding your'e youtube posts, maybe you could describe the electronics a bit more. I assume your transistor controller is a common-base configuration. For the PWM control, I'm not sure if it's good for the MTL units: MTL discourages using pulsed DC and as you not in your video the motor does hum. I'd use about a 25ufd 50V capacitor across the throttle to fix that.

Mark

The Youtubes predate my Snail purchase by a couple of years.

Tests made with stuff I had on hand for N scale. The transistor was from James Kyle's book "Model Railroad Electronic", Tab Books #926, 1977.

I was in the planning stage for my coffee table project; stumbled on the Snails and went that route.

Then noticed MTL said no to "Pulse Power"; but am certain they didn't really mean/know of PWM (back then).

So, really hope my MTLs are good to go with Snails.

Jim

Jim,
I've had no problem with my Snail and any of my locomotives: AZL, MTL or Marklin. I'm unaware of anybody complaining about the Snails.
I can understand the MTL "no pulse power" but essentially a DC switching supply is nothing more than a PWM with a filter on the output.

Mark

Hi Mark!

I hope you post your results for this effort: "I'm interested in characterizing my snail controller next week".

FYI: did a few tests yesterday using Battery Packs of various voltages as input power to my Snails.

It seems to me that just like a model airplane ESC (Electronic Speed Control) FETs are PWM'd up to 100% @ which time the FETs are on 100% of the time.

And that @ 100% speed of the train is much better maintained under varying load such as up and down hill.

The packs I tries were LiPo-2S @ ~ 8vdc, A123-2S @ ~ 7.2 and a single A123 which didn't enough to get things going.

Also, @ ~ 8V my ganged turn-out did not operate reliably.


Jim