Transistor throttle circuits

[Anonymous]

In these days of DCC throttles, this may seem a strange request. I do not plan on using DCC, and remember seeing circuit diagrams and specs in Model Railroader many years ago. Can any one steer me to what months magazine they appeared in? I think it was in the 1980's or so. Or anyone able to Email me information on building a pulse type transistor throttle would be greatly appreciated. A parts list and diagram would be VERY helpful.

Thanks!

[cacole]

The February 1995 issue of Mainline Modeler magazine had a schematic, construction details, and kit information for the High Performance Throttle.

We've been using this throttle system on the Cochise & Western Model Railroad Club's 20x40 foot HO scale layout since 1995 with no problems.

You can find it on the TracTronics Web site at http://www.tractronics.com

[fiatfan]

Another good source of circuits is the Armadillo and Western website, www.awrr.com

Tom

[Anonymous]

Thanks! This was a great help!!

Drake

[Don Gibson]

It could have been Lin Wescott's earlier TAT IV.

[randybc2003]

I have the mag's at home, but not here at my computer. Go to the index on this forum, and look up "Pete Thorn". He was an electrical engineer from California, and wrote several books for K', and had several articles published. Practical Electronic Projects, etc. He wrote "Simplest Transistor Throttle" for MR, and others.
Also, look for "Pacematic" throttle. in the Index.

Have Fun!!! [^]

[pedromorgan]

i wish more of the online circuits were written for strip/vero bpard in mind. i dont have the facility for etching and concidering the chemicals involved i dont really want it anyway.

peter

[Anonymous]

Indeed it was the aeticles on TAT IV. I recall that term. Any idea what issue that was? In the mean time, the Aradillo and Western circuits are very interesting. I plan to build a couple to try them.

Drake

[fiatfan]

Ready the parts list carefully. I found that ocassionally, the Radio Shack part number was off by one or two digits. Purchase by specification rather that part number.

Also, if you have a problem, contact Fred by e-mail. He is very helpful.

Good luck!

Tom

[Don Gibson]

QUOTE: Originally posted by logsnrocks

Indeed it was the aeticles on TAT IV. I recall that term. Any idea what issue that was? In the mean time, the Aradillo and Western circuits are very interesting. I plan to build a couple to try them.

Drake

Contact Model Railroader asking fo any reprint's, and Kalmbach may have published a book just on it. It was a superior throttle.

[SEBASTIEN BOLLE]

   Hi there.

   In the August 1976 Model Railroader, there was an article called "The simplest transistor throttle".

A model rr club I was in used these throttles for going on forty years, and they still work perfectly.

They're well worth building, and have an optional pulse power setting.

Best of luck,

-Sebastien Bolle

[TimReturningMRR]

This article is available on the Model Railroader digital archive which today Maarh 17,2016 is available for printing as the website is unlocked.

I tried to build the Lynn Wescott's TAT IIi which was quite a project and it didn't work.  I'm sure I did something wrong but lost interest in trying to find the problem.  However, I did build a 1 transistor throttle perhaps from this acticle and used it to regulate my N and Z gauge trains from a cheap HO power pack which couldn't operate them at low speed.

The place I plan to use it is to control Walther's turntable built from a kit's motor.  At full 12 volts one can't stop it precisely and at a low enough voltage to be able to do so, it takes too long.  I wanted to build another throttle which would be part of my truntables control panel.

I've lusted after a turntable since the 50's but wasn't ready to spend the big bucks for the assembled one.  I ran into a couple of problems due to imperfect molds on the bogey wheels and the big gear.  I plan to provide a video of what I needed to do to solve the problems but I'm rebuilding my layout and haven't installed the turntable yet.  But I've got it running well on a bench

 

 

 

[gregc]

TimReturningMRR

At full 12 volts one can't stop it precisely and at a low enough voltage to be able to do so, it takes too long.

"The simplest transistor throttle" is where Linn Westcott started his series of articles.   It uses a several transistors as a current amplifier to maintain an output voltage proportional to the base voltage on the transistor.     The problem with the circuit is that without a constant reference voltage such as a zener, the base voltage varies with load.   But it varies less that using a rheostat.

The TAT-III added a circuit to help regulate the base voltage.   But motors have a hard time running smoothly at low voltages.   The TAT-II included a circuit to provide short 60 Hz pulses to the motors to help them run smoothly at low voltages.   In TAT-IV, a circuit providing sharp pulses was added.

I don't understand why Westcott didn't simply build a PWM throttle which provides good low speed performance as well as being efficient, not requiring any form of heat sink.   But back in the early 90s I was told that motors don't like PWM like signals.   Maybe this is true at low frequencies.

A turntable needs good low speed performance for precise positioning.   A PWM throttle provides the best of both worlds and is simple.   Here's yet another example.