Another Keep-Alive Thought

[MarkInLA]

Was just wondering why, if they hadn't then, why, back in the analog, pre-digital-control era of model trains they didn't come up with a keep alive circuit. It's not like there weren't electronics geniuses then...Or did they? Anyone know ? I never heard of it until the last few years. And it's basically really simple, so I hear.
Anyway, even if it increased the price of locos, say $20, I'd like to see it become common issue the way knuckle couplers became, and DCC became.. I really hate stall-outs. I'm sure most of us do...M

[nickelplate759]

They did - it was called batteries.  Capacitors were just too big in those days.  i recall an article in either Model Roader or (more likely) Railroad Model Craftsman  in the 1970s where someone had crammed batteries and (analog) radio control units into a set of HO scale F units.   The name Don Fiehmann (sp?) is rumbling around in my brain.

[John]

Back in the 70s when I got my electronic training, and FCC radiotelephone license those capacitors looked like this ..

[Jim Starbuck]

I seem to remember a thread here or perhaps the Atlas forum maybe ten years ago discussing “electronic flywheels”.

[peteski]

Without going into too much technical stuff, the main problem is the electrical polarity.  But other factors also play a role in such a circuit not being feasible for DC trains which run at variable speeds, and in both directions.

I'm not saying that it couldn't be done, especially with the current state of miniature electronic components, but it woudl be a fairly complex circuit, as large and complex as a DCC decoder.

[MarkInLA]

Thanks, M

[wvgca]

i did make a test unit for DC, but it really wasn't worth the bother .... the voltages, where it really needed them, were too low to be worth while, and diodes were needed, along with a duplicate set of caps, for each direction ...
the keep alive function could be more easily implemented with momentum, in the controller, and only one set of capacitors were needed ...

[MarkInLA]

Toots, I savvy... But I can't see how KA would work from within in the controller..How could that be capable of keeping the motor turning ?
(Funny though; the word 'capable' having a 'cap' in it !)....

[wvgca]

the controller would have momentum, a fancy word for a capacitor, that slows acceleration and delays braking

[peteski]

the controller would have momentum, a fancy word for a capacitor, that slows acceleration and delays braking

Keep Alive circuit (by definition) is there to keep the model running though temporary power interruptions (between the track and a loco). As such, it has to reside inside the moving loco.

There are analog throttles factory-equipped with momentum feature, but if the loco stalls on a switch or dirty track, that will not help any.

[wvgca]

keep alive on a DC loco doesn't really work ..
tried it with regualar caps and supercaps ...

[peteski]

keep alive on a DC loco doesn't really work ..
tried it with regualar caps and supercaps ...

I agree (the 4th reply in this thread).  That was the original question,  but then the conversation turned into "the keep alive function could be more easily implemented with momentum, in the controller, and only one set of capacitors were needed ..."  Since we are discussing DC, to me "controller" meant "throttle".

[wvgca]

the 'keep alive' as origionally designed [on the locomotive] , just couldn't survive the double whammy of size and low voltage ...when super caps were introduced [5.2 volt versions] it solved the matter of size , at least in HO scale .. there was now room for six supercaps [three in each direction], along with the neccesary diodes and charge resistors ...
but the low voltage [especially where it was most needed] was a killer for that circuit ..
Throttle momentum is not a true 'keep alive' as it is not on the locomotive, but it is much easier to implement, as space restrictions are greatly reduced, and only one 'set' is needed ..

[nickelplate759]

Weren't large-ish flywheels considered a mechanical form of Keep-Alives?

[wvgca]

actually yes, large flywheels were used as they helped the motor keep spinning during very short periods of no power to the track ..