Folks, I'm guessing, that if this worked, folks would talk about it. Instead of using a DPDT switch to switch between DC and DCC, I'm thinking of the following: Use DPDT to switch between A) Direct DCC to track. B) DCC through a decoder to the track. I know that switching to B would only allow me to run 1 loco (or a consist) but that's all I'd want to do. I'm thinking it allows me control of locos that are a pain to convert, or ones I rarely run, or... you pick a reason. If it works, is there any detriment to the full DCC coming in on the output side of the online decoder? I'm searching the web, but so far, no luck Edit. I'm doing this, to minimize hardware, because the loops are on a piano, in the kitchen, so the more I can hide, the better. Thanks Marty Sent from my iPhone using Tapatalk
In theory it should work . But it's probably easier to do it the normal way , unless you have to buy a DC power supply as opposed to already having an extra decoder .
A DCC system could be designed to change between DCC and DC (typically it would just be a little more software). You would probably have a better chance of getting such a system form the open-source DCC++ than from a manufacturer. Bob
Yes it will work, ( Been there done that) For simple loops. Just use a larger decoder. Remember the motor outputs would go to the track (orange & gray).
It will work as far as running a DC train on the track......the decoder doesn't care if there are a few extra things between the decoder and the motor. However, you are back to putting DC and DCC through the same track, so you will still need the switch to keep the DC away from the DCC. You are substituting the decoder for a DC powerpack.........what is going to the track is DC either way. Since the DCC components are still connected, you run the risk of frying things if you don't isolate them with a switch. So you aren't gaining anything in that area.......the advantage would be you can use your DCC controller in either mode.
In full support of what MRLDave said. You need to be able to shut down DC completely, keeping it isolated from DCC. Again the simplest way to do this is with a DPDT Toggle. I just went back to reread your original question, "Can a decoder be used to control track voltage?" A decoder was made to control voltage to a single motor of one locomotive or diesel. Not sure why you would want to use a decoder to control track voltage to the track. You'd be better off with the traditional re-sources for track power. Remembering that the decoder takes AC from the track and converts it over to DC to the electric motor. DC is DC to the track and DCC is AC to the track. I wouldn't mess with mixing the two. Unless you like sparks and fireworks...okay...a lot of smoke. Just my two cents and I take change.
Cool. I guess I wasn't really clear, but the more I think, the more I think it would use too much current. I was going to wire exclusively for DCC on a loop. But when I wanted to run a DC loco, I'd switch to running he DCC signal to just one decoder. The decoder Motor output would be to the track. One loco. One loop. Sent from my iPhone using Tapatalk
As long as the DCC feed is isolated from the track when you run the DC, you should be fine. As far as the current, pick up a decoder designed for O or G scale if you want to run multiple engines....for a single engine you should be fine.
What I would be concerned with is voltage drop on the rails as you get further from the feeders. Maybe it will be ok with larger scale decoder.
Voltage drop entirely dependent on load and resistance of rails/feeder, and motor... not decoder. No difference between decoders unless you are running max current, voltage drop same.
What ! The way I see it, you own 1 or more DCC equipped locos, and 1 or more analog DC locos. Would you not have an analog power pack (alla MRC Tech II ) wired to the loop and what, rest of trackage is DCC powered ? What am I not getting ? Gap the rails where DCC will end and DC will take over. Just pay heed to where this gap is. Now have a DPST toggle 'on and off switch' to introduce DCC were the DC is sometimes in use (this loop ), making sure DC is shut/cut off before throwing loop to digital control. No? What ? You wish to be able to do this from a single DCC throttle instead of having to throw a toggle switch mounted in a convenient place ? Maybe I'm way off.. This is what I'm seeing, anyway...And, what some trackage on on a what, piano lid in the kitchen ?! Huh ? ...
If I am seeing this correctly, decoders send PWM to the motor, not DC. Twelve to fourteen volt positive or negative pulses. Pulse width gets wider for more speed. Rich If I am seeing this correctly, decoders send PWM to the motor, not DC. Twelve to fourteen volt positive or negative pulses. Pulse width gets wider for more speed. I have looked at decoder pulse power with a Scope. Some years ago our club which had fourteen blocks wanted to run DC in a couple blocks and DCC in other blocks. Once a loco crossed the gp and we were not paying attention, smoked the NCE five amp booster. Loittle different situation. Rich
You can do it but easy to damage the decoder with an inadvertent short across the rails or crossing into a DCC zone. Does not take much to smoke a decoder. A little different situation. Our club was fourteen blocks with four throttles and when we went to DCC, we tried running DC in a some blocks and DCC in others. One time a loco crossed and before we noticed it, the NCE five amp booster smoked. Banned any more dual operations. Rich
Yes, you can do this. It has been done in the past, there are even articles in the popular press about it. IF you want to do it though, as was stated, good isolation between this and normal DCC is key. Use a large scale decoder and DO DO DO wire in a fast blowing fuse or circuit breaker that will trip before the decoder fries. Also for the record. The DCC signal on a track is PWM, pulse width modulation. The signal to the motor is still normal DC.
Thanks for the flurry of info! To clarify for those wondering. The goal is a single small DCC controller, to control a few completely isolated loops. I swap in a number of small locos, that won't easily accept decoders. So I will use DPDT switches to either send DCC to DCC locos on track, or to a decoder that will send DC to the track, to power the loco. I will look for articles. Sent from my iPhone using Tapatalk
The DCC signal is a modulated, bipolar square wave. The output from virtually all DCC decoders to the motor is a modulated, unipolar square wave The modulation in DCC is to send data as 1's and 0's. The modulation in the motor output, also called PWM, is to control the speed of the motor, as the motor sort of averages the pulses over time to get an "average" of power between the full voltage pulses and the zero voltage between the pulses. There are pretty much no decoders to send DC to the motor, but you could put a filter in to do this, and this has been done in G scale for sure, and of course those components would easily handle your power requirements. Greg
OK. At least for today, it works nicely. I took a TCS HO gauge T1. I connected the track input to the DCC bus. I connected the motor output to a unique isolated loop. I set CV5 to 90. I have great speed control of a variety of manufacturers and models. My power cab didn't show a draw above 0.2A. I'm a happy man. I just need to figure out if I need just 1 DPDT to switch between sending straight DCC to a track, and DCC>decoder>track, or do I need a second switch to protect the decoder, when it's not controlling track voltage. I'd rather know, than take advantage of TCSs goof proof policy. Sent from my iPhone using Tapatalk
I'd disconnect the decoder output too. What about a 4 pole double throw? The first 2 poles can connect the DCC to either the decoder or the tracks... the second 2 poles can either connect the decoder output to the track or disconnect it. To be even more careful, get a center off one, so there's no possible "overlap" between the 2 modes. You can find them much cheaper than this: https://www.amazon.com/Double-Throw-Off-Toggle-Switch/dp/B001PNO3P4 Greg
This link shows what decoders send to the motor. Yes, the motor or volt meter see it as straight DC. I did some measurements with a Scope some years ago. Twelve to fourteen volt positive or negative pulses. https://encrypted-tbn3.gstatic.com/...HBk-Puyfw2X_hx8vuq1fIao8GEL2Qowam7CV3UGQy8Hqv Mark covers this quite well. Kind of technical. https://sites.google.com/site/markg...scussions/decoder-motor-drive/pwm-motor-drive Rich
