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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. |
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19th Jun 2017, 12:39 pm | #1 |
Dekatron
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
Posts: 3,183
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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.
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19th Jun 2017, 1:04 pm | #2 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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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.
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19th Jun 2017, 1:10 pm | #3 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,553
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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. |
19th Jun 2017, 1:40 pm | #4 |
Nonode
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
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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. |
19th Jun 2017, 1:42 pm | #5 |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,687
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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
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19th Jun 2017, 4:19 pm | #6 |
Dekatron
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
Posts: 3,183
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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.
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19th Jun 2017, 8:24 pm | #7 | |
Heptode
Join Date: Apr 2003
Location: Cornwall, UK.
Posts: 989
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Re: Using an electronic transformer for a model tram motor?
Quote:
SimonT.
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19th Jun 2017, 10:48 pm | #8 |
Hexode
Join Date: Oct 2012
Location: London, UK.
Posts: 498
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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. |
20th Jun 2017, 11:07 am | #9 |
Dekatron
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
Posts: 3,183
|
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.
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