Hi folks,
I'm guessing this has been discussed before but I can't find anything. I have an HO layout and now a G scale garden layout, both with DCC. I have some spare HO decoders. It seesm to me that the only thing stopping me using the HO decoders in a G scale loco is the current requirements of the motor and the higher voltage.
It would be simple to build a crude amplifier driver stage to connect between the output of the decoder and the motor. It does not have to have good response, in fact some smoothing of the pulse-modulated wave to the motor would be a good thing. I am trying to find a circuit for a cheap driver: a crude 5amp switching circuit - I don't want to build something that ends up costing as much as a commercial large-scale decoder. has anybody seen anything?
(The voltage is easy to step down into the decoder if it can't handle 22V input.)
I have both HO and G scale too, and personally think it's much simpler and cheaper to just purchase G-scale decoders.
A commercial G-scale decoder is not that expensive if you know where to get them -- try Ulrich Hobbies, Litchfield Station, or one of the other major DCC distributors instead of a local hobby shop.
US$50-80 for G scale is a huge difference to US$15-25 for HO decoders when 5amp power semiconductors are a few bucks each and I already have the HO decoders on a shelf :) I know it can be done cheaper, i am just trying to work out the cheapest!
Okay, please let us know how it turns out. I'm sure others would like to know if it is successful. You may be on to something that no one has thought of trying. After all, the only difference in G and HO decoders is their motor control output transistors.
As usual the devil is in the details. the more I dig in the harder it gets. I think you'd need a MOSFET h-bridge configuration to deal with reversing polarity to the motor for direction changes (i.e. what the decoders have anyway, just scaled up). So if like me you have the HO decoders already it looks attractive but if you bought the decoders it starts getting more marginal.
You are right about the complications. You will need a H-Bridge of high enough current capacity.
I have the same idea as you but never got anywhere.
FYI: Lenz made a LP 200 add-on to the LE230 decoder that did this. It was meant to control a second motor in the engine and only worked with the LE230, but the same design with larger Transistors could do the job on a HO decoder.(see Lenz.com under manuals, discontinued section at LE230/LP200).
Someone with higher skills than mine could reverse engineer this and make it universal. If they do this, I'll be their first customer!
Paul Nevell
You can use HO decoders in some G engines, many single motor LGB, Bachmann, and maybe hartland locos...plus other smaller locos draw no more than 1- 1.5 amps, maybe 2 amps on some. You can test it if you have a current meter and put the engine under stress, you might need to test the stall current. Check out the website by George S.... (can't spell it) here it is:
http://www.trainweb.org/girr/index.html
He has the current draw for many locos. I currently have an HO decoder (1.5 amps - 2 amp peak I think..) in an Bachmann Annie and it works well so far. I know almost all single motor LGB engines can take an HO decoder as well, they use very little current. For USA trains however, you may well need 8 amp decoders or maybe slightly less, they can draw a TON of current. I have an 8 Amp decoder in my PA-1, took advice from others on that one.
Regards,
Ted
I want to apologize for the bad link above in my post, that is the very old web site, the correct link is http://www.girr.org/girr/index.html then find the tractive effort tests, might be under the Technical Tips page. I hope this helps.
Regards, Ted
"... For USA trains however, you may well need 8 amp decoders or maybe slightly less, they can draw a TON of current."
Maybe parts of Paul N. article on the OVGRS site can help ya out. As he strips out a component or two, that are quilty of the large current draw fd within USAT engines, before he installing his REVO 'package'.
ohhhh almost forgot :) here is the link; http://www.ovgrs.org/ If it does not go direct, clik on the side bar "Changes log", and then "Powered - USA Trains GP-7/9"
good luck,
doug c
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