UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Components and Circuits

Notices

Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

Reply
 
Thread Tools
Old 19th Jun 2017, 11:39 am   #1
Tractorfan
Nonode
 
Tractorfan's Avatar
 
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
Posts: 2,590
Smile Using an electronic transformer for a model tram motor?

Hi,
A good friend has asked me to make a speed controller for the 12 volt DC motor in his model tram which will run on just a few metres of track.
I've found a simple, two transistor speed controller, and am thinking about powering it with an electronic transformer intended for halogen lamps. It is a high frequency AC device, and I'm pondering how to rectify & smooth it with bits from my junk-box. Would I need special diodes for the HF? or would IN4002s be OK at that frequency (maybe around 15Khz?)?
If not, I could use the 'traditional' 12 volt transformer from a scrap halogen desk lamp instead.
Thanks.
Pete.
__________________
"Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."
Tractorfan is offline   Reply With Quote
Old 19th Jun 2017, 12:04 pm   #2
astral highway
Octode
 
astral highway's Avatar
 
Join Date: Nov 2006
Location: London, UK.
Posts: 1,819
Default Re: Using an electronic transformer for a model tram motor?

Hello,

That seems a lot of effort for a simple 12VDC supply; how about any old Walwart 12V supply?

If you want to go the other route, 15KHz is far too high to be a suitable frequency for the 1N400X series to deal with, they're general purpose rectifier diodes more suited for mains frequency. You could use Schottky diodes, instead.
__________________
Al
astral highway is offline   Reply With Quote
Old 19th Jun 2017, 12:10 pm   #3
Refugee
Nonode
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 2,251
Default Re: Using an electronic transformer for a model tram motor?

UF400X diodes are what you need.
I looked into model control some years ago and came to the conclusion that the current the motor takes can be used to control absolute speed and provide a speed indicator on the controller.
The motor produces a current waveform that can be measured.
Refugee is offline   Reply With Quote
Old 19th Jun 2017, 12:40 pm   #4
broadgage
Heptode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 860
Default Re: Using an electronic transformer for a model tram motor?

Standard rectifier diodes wont work with the very high frequency AC from an electronic transformer.

I would use copper iron transformer, or possibly an electronic transformer with DC output.
DC units are readily available as some types of 12 volt LED lamp require or prefer a DC supply.
broadgage is offline   Reply With Quote
Old 19th Jun 2017, 12:42 pm   #5
russell_w_b
Nonode
 
russell_w_b's Avatar
 
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 2,470
Default Re: Using an electronic transformer for a model tram motor?

Best of luck... Here's what the output of an electronic transformer meant for powering halogen lamps looks like.

http://www.vintage-radio.net/forum/s...1&postcount=42
__________________
Regds,

Russell W. B.
G4YLI.
russell_w_b is offline   Reply With Quote
Old 19th Jun 2017, 3:19 pm   #6
Tractorfan
Nonode
 
Tractorfan's Avatar
 
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
Posts: 2,590
Smile Re: Using an electronic transformer for a model tram motor?

Hi and thanks for your speedy replies,
I had a sneaky feeling that 1N4002 might not be suitable but wasn't certain .
I could use a wall wart, but seeing as I had a box full of electronic transformers and few wall warts of any use (or with European pins instead of UK ones, which is where the project is destined), I wanted to use what was to hand.
Not to worry, I have a halogen desk lamp that I can rob the iron/copper transformer from.
Thanks again,
Pete.
__________________
"Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."
Tractorfan is offline   Reply With Quote
Old 19th Jun 2017, 7:24 pm   #7
thermionic
Heptode
 
thermionic's Avatar
 
Join Date: Apr 2003
Location: Cornwall, UK.
Posts: 515
Default Re: Using an electronic transformer for a model tram motor?

Quote:
Not to worry, I have a halogen desk lamp that I can rob the iron/copper transformer from.
Good call...! Trying to rectify the output from a halogen transformer is fraught with problems. In addition to the points above, they won't output any voltage until they are loaded. Therefore, you would need to introduce a load on the AC output, before rectification...

SimonT.
__________________
Simon, from the sunny (?) climes of Pasty land
thermionic is offline   Reply With Quote
Old 19th Jun 2017, 9:48 pm   #8
winston_1
Pentode
 
Join Date: Oct 2012
Location: London, UK.
Posts: 148
Default Re: Using an electronic transformer for a model tram motor?

There is no such thing as an electronic transformer, it is a made up term by manufacturers or distributers who don't know what a transformer is. (A device which changes voltage or current by magnetic induction, [or doesn't in the case of isolation transformers]).

Electronic halogen lamp drivers are a (poor) form of switch mode power supply which need a minimum load to work. No way can you rectify and smooth the output as you desire.
winston_1 is offline   Reply With Quote
Old 20th Jun 2017, 10:07 am   #9
Tractorfan
Nonode
 
Tractorfan's Avatar
 
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
Posts: 2,590
Smile Re: Using an electronic transformer for a model tram motor?

Hi,
I realise that it's not a 'transformer' per se, but I used the term to differentiate it from a 'proper' transformer. Indeed, it's a 'driver'.
Cheers, Pete.
__________________
"Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."
Tractorfan is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 12:44 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright ©2002 - 2017, Paul Stenning.