RailPro > RailPro Specific Help & Discussion
RP Keep Alive Installation
William Brillinger:
I have lots of kapton tape in stock now!
Alan:
Had another thought. It is possible the caps are not super caps, just plain ole caps. If that is the case, based on their size in the photo they may not have enough capacitance to run a 600mA load long enough to be noticeable.
What value are the caps? It will be marked on them. I can't see in your pics well enough to determine.
emd_16645:
--- Quote from: Alan on October 03, 2018, 06:57:47 PM ---Had another thought. It is possible the caps are not super caps, just plain ole caps. If that is the case, based on their size in the photo they may not have enough capacitance to run a 600mA load long enough to be noticeable.
What value are the caps? It will be marked on them. I can't see in your pics well enough to determine.
--- End quote ---
1F 2.7v. Labeled 1802 PET if that means anything.
Alan:
1F is a super cap. Since they are 2.7V then they must be wired series to work in a 15V circuit (2.7 x 6 = 16.2). Six 1F caps in series = 0.166F or 166,660µF which is a lot of capacitance.
If we assume the supply voltage is 14.8V and the LM will turn off when the voltage drops to 10V and the motor has 24.6Ω resistance ( 14.8V / .600mA = 24.6Ω ) then 166,660µF should provide 1.6 seconds of full load operation. This is ideal world calculation. Realistically you should expect about 1 - 1.5 second of operation.
At this point the only logical conclusion is a fault in the wiring - incorrectly connected, cold solder joint, broken wire or board trace, etc. If you place a voltmeter on the capacitor leads while the loco is on powered track (0% throttle) what reading do you get? System voltage? What reading do you get if you turn off the track power? System voltage that slowly falls away? Same two scenarios and questions with the voltmeter connected to the LM common (blue on 9) and negative (yellow on 6) leads?
emd_16645:
Alan,
Supply voltage is 13.6 VAC (DCC powered layout)
I am getting 13.5 VDC across the LM3. When track power is removed it drops to 1.69v rapidly (within a second) and holds.
Across the cap bank I’m getting anywhere between 2.4v and 11v at normal state, with no apprarent consistency. Voltage drops off immediately if track power is removed. Looks like I need to get into contact with the manufacturer.
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