NEW Update Easy DIY Keep Alive (126)

It's been a couple years since I filmed the original video on this subject so it's time for a remake. I'll share with you how I make these and give you more tips on how they work, what components to use, and hopefully get you started on the road to making your own. Below is a list of components and sources.
Super capacitor 3V 1F #581-SCCR12E105SRB Mouser.com
Resistor 100 ohm 1/2W #293-100 AllElectronics.com
Diode 1A #1N4001 AllElectronics.com
Zener diode 12V 1W #1N4742 AllElectronics.com
Battery Shrink Wrap 29.5mm PVC Amazon.com

[@nathanadams3191]

Clear, thorough, and helpful. Thanks, Larry.

[@mandbhomestead]

Great video again Larry, full of lots of info and tips. You make this look very easy also. Thanks for sharing and stay safe. Ken

[@donaldatherton86]

Thank you very much. Your explanations were very clear and understandable.

[@charleswalsh9895]

Terrific video lots of information

[@MikesProjectsandHobbiesMC]

Ive been building them for a while now, great how too video. Probably the best part about building your own is being able to build them to fit. I use four 2.7 super caps and have been able to fit them inside just about any tender or loco. If you can fit them close together you can still use 32gauge wire between them. It really helps when trying to make them "fit".

[@mcrow3856]

Thanks for this. I made one and it works well.

[@spacecalander]

i just use extension lighter, works great and doesn't burn your hands. Great close up.

[@BillMastersMRR]

Finally got all of the components I need to try making one of these. Works great! It's kept one LED powered at full brightness for 20 minutes. And an ordinary hair dryer does work on the heatshrink :)

[@w.rustylane5650]

I build my own stay alive circuits. I use a mini full wave bridge rectifier (the little square ones), a 3300uF capacitor @ 25 volts DC and LED strip lighting. I got all my components from China as they were the most economical. The LED strip lighting can be cut apart at every 3rd LED and have the ballast (current limiting) resistors already installed on the LED strip and are 12 volt. I also make my own pickups out of copper salvaged from an old computer. I only use these components since my trains are DC only. The LED strip lights have adhesive on the back so it makes it easy to stick to the interior roofing. In a couple of engines I've even used magnet wire (varnished wire) and will still carry 12 volts DC. Cheers & 73 from W Rusty Lane K9POW in eastern Tennessee

[@brianmuhlingBUM]

Easy! Thank you. 😊

[@bobsmodelrailways]

Hi again Larry. The components as you make can be located anywhere - not necessarily in the locomotive. In my shunters (switchers) I have a permanently connected “match truck” and put the components in there covered with a Tarp. The cables can then be wired to the decoder via the coupling.

[@gs425]

Just remember that when you put caps in series you REDUCE the total capacitance. So 4 x 1 farad caps means total of 0.25F. Therefore if you want to compare with same rating single capacitor for size, compare against a 12v 0.25F . However as these type or normally cylindrical they are typically harder to fit than 4 smaller ones side by side.

[@Mike__B]

True, but you increase the voltage by the same amount hence the total amount of charge they can hold doesn't change.

[@daverahn1711]

@@Mike__B his point is that if you add a 12V .25f cap, that you don't need multiple, you can put them in parallel if you want more capacitance.

[@Tom-vd1kr]

I have built your DIY current keepers which are super. Have you ever looked into the Circuitron Snapper Switch Machine Power Supply?

[@jimheath3337]

Hi Larry, thanks for all the great videos! Will these work for esu v4 and v5 decoders? Thank you.

[@TheDCCGuy]

Sorry but I din’t recommend it. Those use a 3 wire stay alive connection with one wire that turns it off during programming to prevent damage. If the ESU PowerPaks are too large or expensive check out those from DCC Concepts with 3 wires. Iron Planet Hobbies should have some.

[@georgebell8241]

Good video Larry will the stay alive help with lighting up a caboose or Passenger cars thanks

[@TheDCCGuy]

See my other videos on lighting stay alives.

[@bravedan]

Good Video, thanks. It's implicit that the 3v 1F size will prevent use for much "N" gauge UK steam use. However, I have a "N" gauge tramway in build where the double deck old trams offer some space above the motor, etc, in the upper deck area, but these components will not fit. I ONLY want to provide cross gap operation, I do NOT need lights or sound or lengthy duration beyond say a couple of seconds. Any advice please?

[@TheDCCGuy]

As I have said the TCS KA1&KA2 keep alives are the smallest option I have found. However take a look at the stay alive products on the You Choos website (www.youchoos.co.uk/Index-Shop.php?L1=StayAlive). I have not seen any of them but there may be an option. One option with an N scale pair of locos is to put a decoder in one loco and the KA in the second and power them both off the single decoder. Otherwise your best bet is to build bulletproof track with lots of track feeders, keep your rails clean as a dinner plate, and power your frogs. Also you should regularly check your electrical pickups on the loco to make sure they have not collected a bunch of dirt, grease, and lint or gotten bent out of shape. I experimented with N-scale modules around 2003-4 and got pretty good performance following those guides and that was before we had stay alives so it is possible.

[@railbuilderdhd]

Nice update to a good video. One question from a newbie point of view. If I install these in my locomotives will I still need to power the turnout frogs or would this fix that problem; If not completely mostly fix the problem?

[@TheDCCGuy]

They should get you over any dead frog.

[@railbuilderdhd]

Model Railroading With The DCC Guy Thank you for clearing up my thinking on this. I figure I could use these first then later wire the frogs if needed.

[@andrewkeeney701]

Very interesting and helpful, Larry. Do you know if there are newer and smaller caps available since this video was created? If so, any specs for us to use to order them? Thanks, Andy K

[@TheDCCGuy]

I have seen some smaller ones in the TCS products but they are unmarked so I don’t know their ratings and I can’t find them anywhere. There may be some out there but to be honest I haven’t had the time to search for them, plus with all the component shortages I bet getting them would be a PITA if possible at all.

[@andrewkeeney701]

@@TheDCCGuy thank you, Larry, I appreciate the quick response. I agree completely on the hard to get. I have friends that have been waiting several months for NCE components. Thanks again, Andy K

[@dalecherne5377]

Would a higher Farad rating per capacitor work also? Or do you start running into the size problem like you were talking about?

[@TheDCCGuy]

I haven’t looked at anything with a higher rating than the 1F ones.

[@bcck8501]

Hi Larry, Would it be possible to use tantalum type capacitors. I would imagine that it will be much smaller? Thanks

[@TheDCCGuy]

No, you need something with enough storage capacity power the decoder and the model.

[@repeters1]

Hi Larry, I made a few of your other super capacitor keepalives for passenger cars and cabooses (cabeese??). I was looking up the Zener diodes and when I searched for Zener diode 12V 1W, I got 1N4742. I then searched for 1N4642 and came up with only a data sheet posting it was 27V, 0.6W. Will the 1N4742 work? Thanks, Pete.

[@TheDCCGuy]

It appears I made a typo in the parts list and the Zener I used was a 1N4742-thanks for catching that. At any rate in video #31 I discussed how all this stuff works and considerations for substituting components so you might take a look. The role of the Zener is to act as a sort of voltage regulator which prevents the capacitors from being overcharged. So you have to keep the Zener rating lower than the total voltage of the caps. With four 3 volt caps that means a 12 V rating. With 5 caps that is 15V. The Zener keeps the charging voltage below its rated value. Now if you can guarantee that the track voltage will NEVER exceed the total voltage of the caps then you don’t even need the Zener-but if it does you’ll create a short lived smoke generator.

[@GrandsonofstFerdinand]

nice video! its defiantly cheaper to make these than to buy them premade. I have a question though. I have 4 lighted passenger cars equipped with the Digitrax DN136 decoders running led strip lights cut to fit soldered to a 10k Trimmer Potentiometer and of course no motors installed. where would I install the caps? on the input of the potmeter or before the decoder?

[@TheDCCGuy]

You would install it the same as if the decoder was attached to a motor.

[@GrandsonofstFerdinand]

@@TheDCCGuy thank you!!!

[@2011Maynard]

Hi Larry - 1 comment and 1 question. Have made several of these at 15v from your previous videos, and they work great. Question... A few months or so back you were researching adding a Keep Alive to Loksound - that still on the RADAR?

[@TheDCCGuy]

Yes, that’s on my radar but for some reason the radar screen keeps growing.

[@dalecherne5377]

Do you mean each capacitor is rated at 15v? Or do they all equal up to 15v?

[@TheDCCGuy]

They are 3V each so with 5 you get 15V, with 4 you get 12V, etc.

[@georgegillespie5746]

Hi Larry, Digikey has these caps: SCCQ12E105PRB KYOCERA AVX. Smaller diameter (6.3mm vs 8mm), same 1F and 3V but different tolerance range (-0 +100%). Are these a usable substitute for the SCCR12E105SRB?

[@TheDCCGuy]

They look comparable to me.

[@mikegegner8846]

Hello Thank you for your instructions. I model in g scale using just dc not dcc. Can I use the same components, or do I need a I higher voltage components. Thanks Mike

[@TheDCCGuy]

Sorry Mike but these only work with DCC.

[@GudrezBilly]

The big problem with DC operation with capacitors is if you kill the throttle, the locomotive would still have power and therefore would keep going until the capacitor runs out. Great if you hit dead spots, not great if you're gonna hit something or derail on a switch.

[@Vman7757]

Thank you for this video. I have made circuits for my own use in the past. These look to big for N scale. Is it possible to make these even smaller? I would be very interested.

[@TheDCCGuy]

Unfortunately the size is controlled by the number and size of the super capacitors and these are the smallest I can find with these electrical capacities. TCS uses a slightly smaller cap in their new ones but I have no idea where they get them or their ratings as they are in a plain, unmarked package and they aren’t sharing trade secrets.

[@Vman7757]

@@TheDCCGuy I am retired from the electronics's field. I put in Thirty seven years Programing and working on fixing computers. I did use super capacitors a quarter the size of your smallest capacitors you used. But I have no idea how to find them or if they will work to make one. Or even if it all worked out be cheaper than just buying a ready made. $26 is not a bad price. But times 200? Or 263? That is $6,838. Okay maybe I can't do them all, LOL But it's your video that got me thinking I can do this. I have made other usable circuits before in my past. Thank you so much for sharing. If I do come across something I will be sure to pass it on. LOL Like other projects on my table it maybe a while. LOL

[@Vman7757]

@@TheDCCGuy Well I got a KA1 for $20. I will try it out. See what I get. Thanks.

[@blueridgebonsai9155]

@@Vman7757 Great, but tell me where you found it for $20!

[@Vman7757]

@@blueridgebonsai9155 At my loco Hobby shop. Near where I live. The owner knows I do N scale installs, and Paint and weather for some of his clients that come in. He gave me a discount.

[@ibsteve3]

What gauge wire are you using for the main leads on this circuit?

[@TheDCCGuy]

Not rocket science, probably left overs from decoder wire clippings.

[@ianmcgee9945]

Can you get a keep alive for a 12V DC loco? I have a couple of small 0-6-0's that would benefit from one over certain sections of track that have multiple turnout frogs right next to each other. Or would one of these work on 12V as it is? I have no plans for DCC in the immediate future.

[@TheDCCGuy]

Sorry Ian but these are DCC devices and I don’t know of anything similar for DC.

[@ianmcgee9945]

@@TheDCCGuy I was afraid of that! Oh well... By the way, I'm a new subscriber from Canada to your British channel. Thanks for the great videos. It's nice to see some British content from the North American perspective.

[@hansfriess]

Is there a way to make your own DCC sound decoders?

[@TheDCCGuy]

Yes, but you’ll need a degree in electrical engineering, a complete electronics shop, and the ability to go out and record all the sounds that go into a sound file. In the long run I think you’ll find it is cheaper to buy the commercially available ones.

[@markturner6240]

So? Wanted to ask, would a 1 watt 100 ohm resistor be ok? Or has it got to be a 1/2 watt? Thanks.

[@TheDCCGuy]

1 watt is a bit bigger but it should do the job and then some.

[@markturner6240]

@@TheDCCGuy lol! Its Way bigger, but that was what they had at Mouser, so I ordered. Thank you very much for doing these videos, the information is priceless! Do you have a video on the subject of hardwiring a KA to the older style decoder? Soldering instead of plugging? Thank you again

[@TheDCCGuy]

Try video #32.

[@M0Liv]

What prompts you to assemble all these components in lieu of simply wiring up several capacitors in parallel?

[@TheDCCGuy]

Series wiring adds the voltages to get enough to power the decoder and locomotive.

[@mach37]

This should work with DC, too. ?? But not as big a problem if you don't have to keep DCC decoders "alive."

[@TheDCCGuy]

No, they are for DCC only.

[@mach37]

@@TheDCCGuy -Rats! Well, I will be 90% DCC anyway, by the time I get trains running.

[@adfgfds]

Curious: How cost effective is it building your own vs buying a pre-made one?

[@TheDCCGuy]

I have never done the math as it changes with the cost of the parts. The most expensive parts are the capacitors, so it mainly depends on how many of those you use and what the current price of those is.

[@pillaroftruth2830]

where do you attach a DIY keep alive to a digitrax DH123A?

[@TheDCCGuy]

These were discontinued 10 years ago, long before Digitrax started providing keep alive connections. You would need to remove the blue plastic wrapper a d explore the circuit board for the negative co tact. I discussed this in my video #32 on making the connection.

[@pillaroftruth2830]

@@TheDCCGuy Thank You have have watched that video and I ordered a microscope type bench top viewer with light to get a very close look at the decoder. Eyes are not what they used to be. Thanks for addressing my question.

[@DavidBelman]

Why does the 100 ohms 1/2 w resistor get too hot? I am using super cap 2.7 V 1 F, Zener 1N4001, Zener 13 V 1 w and a soundtraxx decoder

[@TheDCCGuy]

Not sure. How many super caps do you have in line? Which decoder and how many amps is the motor drawing? I have seen some circuits that use a full 1 W 100 ohm resistor so you might go with that.

[@DavidBelman]

I am using 5 super cap online, I have an ECONAMÍ PNP, I do not know the motor amps, the locomotive is an Atlas,

[@TheDCCGuy]

OK, that sounds fine. But now let me asked what your track voltage is? This circuit assumes a track voltage of about 13 V and will regulate the voltage your caps see to that so they don’t overcharge. But if your track voltage is much greater than 13 V then your resistor will need to work harder to take care of the difference.

[@DavidBelman]

My track voltage is 15 volts 3.5 A, I have MRC PRODIGY ADVANCE2 DCC SYSTEM

[@DavidBelman]

Output : DCC SIGNAL WITH 14.5 V AMPLITUDE

[@wheelhorseman2306]

Hi, Larry. Good video, I was able to build these with confidence, but I can't get these keep alives to work with my Digitrax Zephyr Express- they keep triggering a "Booster Track Fault" error. It appears that they draw too much current and "look" like a short circuit to my system. I tried bumping up the size of the resistor from 100 to 220 ohms without success. If I build it then add a 10 ohm resistor in front of the blue wire, I get smoke! I looked at all of the videos about these, and triple checked my components against your list- all identical except my Mouser Zener diode is 12V, 1.3W. I doubled checked the diagrams and my connections and everything is hooked up correctly, but none of the six I built work. Any thoughts? Anyone else have this issue? Thanks for the help...

[@TheDCCGuy]

You were correct to try and limit inrush current and I am surprised you are having issues. Assuming you wired it up correctly I cannot figure out what the issue is. I have tested these previously on 3 amp systems.

[@wheelhorseman2306]

@@TheDCCGuy Thanks for your reply, Larry, appreciate it. The Zephyr Express is pretty new; I was wondering if Digitrax changed some limit on what is a fault triggering current? Maybe my DCC system is faulty? I'll try sending Digitrax an email next week. (I'll roll my eyes if they tell me that's what happens when you don't use the Digitrax brand of keep alive). I stopped at my local hobby shop but they didn't have any Soundtraxx CurrentKeepers in stock. I'm ordering one online, and if it works, I'm going to open it up and see what's inside. (I got plenty of shrink wrap). The Soundtraxx video says they use five 2.7V caps, and he mentions a voltage regulator, I'm guessing it's a 13.5 V zener diode. Again, if anyone out there is using a Zephyr, are these homebrew keep alives working for you? Thanks.

[@wheelhorseman2306]

Larry, I tested the assembled keep alives and they are working fine. I hook them up to a small HO DC power pack, and they charge to 12V and discharge just fine. I'll probably be sending my DCS 52 Zephyr back to Digitrax for repair. Sorry for the confusion; I'm just more suspicious of my amateur work than their factory's. Thank you!

[@wheelhorseman2306]

Found the problem- a single strand of fine gauge wire was in the plug housing on the decoder chip; when I plug in the keep alive it shorted, unplugged and removed, it opened. Darnedest, freakiest thing and I wouldn't have thought it could even happen that way. The plugs I got on Amazon are 1.0 mm JST plugs, I paid about forty cents a piece for them. Of course the colors needed to be switched- the black wire to blue, and the red wire to black, but I couldn't give Soundtraxx $8.00 just for their plug.

[@TheDCCGuy]

Glad you tracked it down. Those little whiskers are very hard to spot but can create a short just the same.

[@adey2318]

Hi I’m new I’m looking for where can conected one of this on DCC decoder digitrax DH126D if some one know please let me know

[@TheDCCGuy]

What model do you have and does it have a DCC socket.

[@adey2318]

@@TheDCCGuy I don’t sure what you asking for all I know it is a DC loco and I conecte e digitrax DH126D on it the most sheep Decoder I can get it work great for me it is just wire form pick up to decoder and conecte from decoder to motor and light

[@adey2318]

@@TheDCCGuy I don’t know if you ask me de model for the loco I have Lima ICE-T w/ Pancake motor and this is why I need the stay alive it have only 4 wheels pickup ,2 for each side and it is hard to keep runing on turn out or slow speed PD sorry my englis

[@caseyjones745]

It appears that you are using a Zener Diode in this example for the same purpose that you used a Buck Board in "Lighting Caboose & Passenger Cars". The Buck Board is adjustable, whereas a Zener Diode is not, but if you now the maximum voltage of your capacitors, why would you need and adjustable Buck Board?

[@TheDCCGuy]

It’s just easier and probably cheaper than cobbling together another circuit.

[@frankhellman6879]

One down vote from the guy who still swears by DC only.

[@MikesProjectsandHobbiesMC]

Its amazing they are still around. Wonder if the have a VCR and a CRT TV? :-)