Great video David. One suggestion I have for anyone struggling to find room to fit a large capacitor is instead to look at using multiple smaller capacitors distributed around the loco. Connecting them in parallel will give a total capacitance equal to the sum of the individual capacitors but without having to find a single space big enough for one very large cap. For instance 3x 4700μF connected in parallel will give 14100 μF (very nearly as much as the 15000 μF used) but it may be easier to find 3 spaces for these physically smaller devices.
Very nice David, I suspect there will be a lot of people out there that will not be able to solder onto such small pads, but never the less excellent video...Simon
Thanks, Simon. Yes. It definitely needs a steady hand and confidence with an iron, but I actually found it easier than soldering on ESU's Powerpack mini to their loksound 4 micro (now, those really are small pads!).
Thanks, Sean. Really appreciate the feedback. I'm currently sorting our my spare room. Once it's cleared, I'll be able to set up my spray booth and hopefully get a wee bit of weathering done too. I've always preferred Bachmann and Heljan because of their detail and features, but if you spend a wee bit of time on these lower spec ones, you can get them looking a lot better. 🙂👍🏻
Hello there great work! what type is the capacitor and the resistor and diode please! I have a TTS Hornby valenta decoder in my HST that I have consistently cleaned the wheels and track and the problem was the wait for it ! point frogs .. the hornby valenta decoder is R7140 i am going to do the same as you. I used to work in an electronics factory back in the 80's (Burroughs computers) where i built the PCB boards for the Disc drives from scratch..
hi, is it possible to use 2 o r3 capcitors inline, i have 2x 10v 6800uf capacitors, 100ohm resistors, and 1n4001 diodes,,,, excellant vids by the way,,
Hi. If you hook them up in series, the charge across each capacitor will be the same irrespective of the capacitor rating, although you will have more storage capacity overall. Also, so long as they are in series, they will decide the voltage across them, so while you mustn't use 10v capacitor with DCC or even DC track voltage generally, you could probably get away with two or three in series, yes. But I would definitely test the circuit first before installing it in a model, just in case it runs hot or explodes. Capacitors can fail quite spectacularly!
brilliant video. just ordered some components. how would this be wired into a decoder which has got a 3 pin stay alive connection? what's the 3rd pin for?
It really depends on the model of decoder. Some require three wires, with one being for logic. Others have three wires, but can be used without logic. The instructions with the decoder should explain what works with that decoder and also how to wire it up. These stay alive units are basic units with/which work well with many decoders, but they may not work with all decoders that require a logic level feedback from the stay alive unit.
Hi thanks for the video. 1 question. how do I choose the right patametets of resistor and diode for given capacitor. u say use 100ohm and you ll be fine but why 100:-) thanks a lot
What is the purpose of the resistor? I would have thought it would have defeated the purpose of the diode? Creating your own stay alive capacitor is a good idea
Hi Brian. It's to do with the direction of the diode. In this circuit, the capacitor charges through the resistor because the diode acts as a shut value when the current is flowing in that direction. When it's keeping the decoder alive, the capacitor discharges via the diode, which is open in that direction provides less resistance than the resistor. Does that makes sense? It's always easier to describe in a diagram rather than text!
Hello. If paralel to the capacitor Zener diode 15V, 0,5W will be added. In this case capacitor can be 16V and they are smaller than 25V. Can stay alive be done like this? best regards
So what capacitors would u use for class 50s 47s 33s 20s etc if the larger one doesn't fit as I have a few heljan and hornsby locos that I want to do also if u change the capacitors to smaller ones do u still use the same resistor and diode sizes
Yup. The for this sort of unit, the resistor and diode can remain the same. Re. the capacitor, in practice it really comes down to the biggest one you can fit in. Different manufacturers make them different sizes, but same capacitance value, so if you shop around, check the dimensions and you may be able to squeeze a reasonable amount in. Anything below about 4700uf, and I don't thi k you'll notice anything much different with a sound decoder.
Hi Rob. Many thanks for the comment. I actually designed the stand myself and printed it on my 3D printer. After knocking over a full bottle, I learned my lesson. I can make the 3D file available, if you'd like?
Hi David , i have a Lima class 37 with a CD Motor fitted , i have also fitted a TTS Sound chip -- i then saw your video regarding fitting a stay alive . having purchased a DCC Concepts large capacitor and followed your video with great care. i fitted the unit . Since fitting the sound now is very low -- and the loco will not move it just sits there and clicks !!! If i turn sound off the loco moves , since removing the Capacitor and turning the sound on it clicks , WHAT DO YOU SUGGEST ------ I did ask if you could fit this for me but you said you were too busy --- is there any chance you could now you could look at it for me ---- im in no rush to get it done ,BUT i would like it sorted.
Hi John. This isn't an issue I've come across, I'm afraid. I've done a few of these modifications now and they've all worked fine from the get go. What rating was the capacitor and did you also put the diode and resistor in the circuit? Are you sure you connected it up to the correct pins on the decoder? Did you manage to get the wires soldered quickly or is there a possibility that you applied too much heat to the pcb or disturbed any of the other components? If you're able to send me a photo of each side of the decoder, I'll certainly take a look and see if anything obvious jumps out, but it's possible that the decoder is now permanently damaged. They are really quite delicate bits of electronics and when they fail (particularly with tts chips) unfortunately there is often not a huge amount that can be done.
Hi David, i know this video is quite old but I’ve just installed some lights into a coach of mine but they keep cutting out at one specific point and turning back on about 40cm down the line. Oh and btw if i turn the function off and on on my controller after it cuts out the light comes back on. None of my other loco’s or coaches have any problems there
That sounds very strange indeed! Normally, if it cuts out at the same point all the time my first guess would be the track, but if other models don't cut out there, it's less clear. I wonder if it's an overload issue? What lights are they? What decoder are you using? Are the ones that work long or short wheel base models, and what's the coach?
Strathpeffer Junction Hi first off Thanks for the quick reply, i’m not sure if it could be overload because all the other trains keep running even if the lights cut out. Or now i think of it do you mean a decoder overload? It has 3 lights 2 of which are red led’s for the taillights and one yellow ish lightbulb the coach came with. The white one is wired up to function 1 and the 2 red leds to function 2 and of course both positive wires connect at the common blue. Its using the Uhlenbrock 76900 function decoder. The coach with the problems is long wheelbase with left pickups at the front bogie and right pickups at the rear one. I don’t have any block detection so that can’t be related either. The other loco’s and coaches are mostly short wheel base. And its an old lima coach no real specifics.
Just to be clear the led’s have been bought from a model shop and they told me to “just attach the red to the blue and the black to the function pad on the decoder. No resistors or anything needed as far as i know this us one of the first times i’m doing this kind of stuff so i might just be stupid
Hi, i was wondering would this concept work on DC locos, it makes sense to me but just wanted to double check before i actually go ahead and buy the components, also if it does work would i still need to use the resistor and diode ?
Hi Lorenzo. I think the issue you'll have is that dc uses the polarity of the track feed to set the directiob of the loco. Capacitors are also polarity dependant. You would need to devise a circuit that stored energy depending on the direction of the loco - probably with two seperate capacitors - and then gave back the energy correctly. It would be a more complicated circuit to the dcc stay alive circuit. The resistor and diode are there to protect the capacitor and guard against inrush current. You'd need something similar for anything where a capacitor is used.
You can sort of do it; the main difference is that you need an non-polarised capacitor which can supply the motor in either direction. Non-polarised capacitors are too small, but you can make one from two electrolytic caps back to back. I've been experimenting with an old Hornby smokey joe with 4 1F 3V supercapacitors in; it works, but it actually runs for too long once you kill the power, so I've been meaning to try smaller capacitors instead. You don't need the diode or resistor; it must be able to provide full power in either direction to run the motor. It will have a high startup current, but this doesn't really matter with DC as it will only be one loco at a time. You just need enough caps to accept the maximum voltage, paired back to back like +c- +c - -c+ -c+; nothing else is needed other than the wires. Give it a try. Probably not with your best loco, though :-)
I used capacitors on direct current (DC) for filtering low frequency, I.e., speakers, and capacitors act differently for Alternating Current (AC, and in this case alternating square wave DC pulse)… I’m more f a programmer than engineer these days, so correct me if I’m wrong… anyway… great video that is still relevant over the years.
