Model train throttles? - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th November 2007, 09:39 PM   #21
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Quote:
Originally posted by EC8010


I wasn't intending to tease. As has been pointed out, there are two main problems with model cars and trains. Intermittent high resistance contacts and stiction. The solution in both cases is the same; short high voltage pulses. Of course, it's not going to be EMC compliant (not with those pulses connected to an aerial), but it will give good control. What you would need would be a line scan valve as your series pass element, driven by variable width pulses from a 555 or similar. A simple triode amplifier between the 555 and the PL519 would suffice. Poor smoothing before the controller would be useful.

The 317 approach is the exact opposite of what is needed.
I use homebrew PWM with my model trains (another foamite revealed ) I generally use big mosfets or bipolars. 556 makes a cheap and nifty PWM controller with a small number of parts. Hint: Use the second timer as a comparator looking at the fixed rep rate ramp generated by the first.. Incidentally a 40 - 50Hz repetition rate works great with just about every motor I have tried. Performance seems to diminish above 60Hz or so with typical can and older style open frame motors.

Maximum voltage at 100% duty cycle should not exceed the dc voltage rating of the motor to avoid overheating problems. Use sweep tubes for power elements (CF) if you must use tubes, and put them inside a feedback loop with an op-amp (OPA445) to control the output voltage under varying loads. (Open circuit voltage hazard otherwise.)

PWM results in oodles of torque, guaranteed starts, and good low speed operation. Buzzing at low frequencies is minimal. Higher frequencies result in inductive instead of mechanical integration in the motor and produce lower torque and a lot more noise. I dream of diy dcc someday..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Model 1 Harderror Full Range 10 10th May 2010 01:35 AM
Train Horns? lochness Multi-Way 0 12th October 2007 05:47 AM
Mod Cyrus II power train for PSX? enthusiastor Solid State 20 27th June 2007 03:35 PM


New To Site? Need Help?

All times are GMT. The time now is 12:28 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2