As I understand it, it is possible to run some DCC decoders on DC power. I have an old Tyco GP20 that I've been able to restore and rehabilitate to good running order and repainted the shell as a Norfolk Southern. However... Since the motor is an old metal pancake type, it is not possible to isolate it from itself. So...since this engine is relegated to the DC layout, and understanding I will not be able to control the motor with a decoder, I would like to find an inexpensive decoder that will operate on DC power to control the lights only. Will this work?
Not really The decoder power source will be the track and this voltage varies from zero to 12v dc. It will also be electrically noisy. The lamps intensity will vary with Loco speed and at some point the track voltage will be too low for the decoder to operate. The decoder would not like this and the decoder micro/eeprom could get corrupted. Ron
I meant to add that I will be refitting the engine with LEDs. Since posting this I looked into the TCS FL4 and there are configurations enabling DC operation and Analog (DC) Power Control. More research to do.
Yes, as far as I know, every current production decoder can be run on DC. Yes, it would work. In fact, Atlas used to sell Locomotives with decoders that had a jumper for DC operation where when you moved the jumper the headlights were still powered from the decoder.
Are you sure? Here are a couple of DCC installs in Tyco's with pancake motors: http://www.tcsdcc.com/Customer_Cont...o/ALCO CENTURY 430/TYCO ALCO CENTURY 430.html http://www.tcsdcc.com/Customer_Cont...o/Alco Century 630/TYCO ALCO CENTURY 630.html
Yes - but only if the DC is above a certain voltage. This could be approx 7volts. Below this, the decoder regulator output will become unpredictable and could cause the decoder to shut down. Decoder supply voltage specs will need to be checked.
This is good news! Had gotten different opinion on other forum; to remain unnamed. I had missed this on the TCS site. Thanks so much for the info.
When converting an old DC engine to DCC, I assume you'd need to determine the starting voltage of the motor. Can this be done with a multi-meter?
The multimeter requirement is current required at 12 vdc with motor stopped. Most decoders seem to be one amp, some 1.5 amps. I do know one company has two amp but are sound decoders I believe. I have done a Bachmann HO pancake motor using a DZ125 decoder. Worked ok but the pickups needed a lot of help. I could not tell what the OP's motor is like in the loco diagram. I have done a decoder with no motor but I needed a 100 ohm, 1/2 watt resistor so my DCC system could identify the decoder. I had to do some fine tuning to keep the resistor from getting hot. Rich
No, there is no need to determine starting voltage when doing the conversion. If your decoder has Bemf compensation and you have it enable and set correctly, then there is never any need to determine starting voltage because the decoder will determine it on it's on. Without Bemf compensation you still don't have to determine it, but if you want the loco to start moving at or near speed step 1 then you will; however, you do this after the conversion through trial and error.
The decoder uses the motor load to send an acknowledgement to the DCC system. That load, and hence the resistor if no motor is present, is only needed if you want to read the decoder, it will program and operate without it. When programming, if writing an extended("4-digit") address, depending on the DCC system you may have to do the three writes (CV17, 18, and 29) separately. This is because the system may stop programming and report an error after the first write when it doesn't see the acknowledgement from the decoder.
Since you are using LEDs you might like to make your own decoder. The low power DIY function decoder at dccdiy.org.uk which you can make yourself operates the LED lighting at 5V so it comes on at full brightness at low speed. There are two versions with either three or eight function outputs depending on how much room you have.
