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Wired the components on a board to make the final installation have a neat look. Starting cold slowly bringing up track voltage, the lower the track voltage the longer it takes the boost board to reach its peak setting, no drawback there as once the caps charge and the sound sees 5.5V it starts. Made my own rectifier using diodes I had on hand, 1A. Your estimate of using a 3A is more like it. If the track voltage isn't raised very slowly, they are heating and causing very quick and sharp shorts. By using the battery input leads, keeping the I/O switch in the loop, you can turn it off and the caps will hold the charge until next time turned back on. My next bench play I'll replaced the under powered rectifier I assembled with ones on the way. Would also like to wire a relay (the 6V from the other print) coil with the limiter output. Then use the contacts in place of the switch. The relay is after the limiter so it should recover next time the circuit sees 6V. Any thoughts??
EDIT: forgot to mention I substituted the limiter with one that doesn't have a V meter built in.
 

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toddalin, testing showed the way I described wiring the I/O switch is not such a good idea. When left as built when track power is lowered to 4V the unit will continually operate. When track power is removed the unit will continue to produce sound for 75 seconds then the board times out. The caps actually produce a very low crying sound as they slowly discharge, and I can hear it. If the switch is turned off at that time the caps will hold the charge and start right up when turned back on. When I wire it as I described above, the relay coil wired to the limiter output, and the I/O wired through a contact in the really as soon as track power is dropped so does the relay, contact opens and the sound stops immediately, not what we want. Next test is to wire the relay coil to the caps and the contacts still wired as the switch. As the caps 'cry' down to below 6V the the relay would open, turning off the switch. Resuming power to the cap circuit should close the relay turning the switch back on??? Sounds good on paper, real test will be next time at the bench. Open to all thoughts and suggestions.
EDIT: that will not work either, the relay coil will ultimately drain down the caps, unless the cap circuit is opened as well?????????? Still scheming.
 

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Discussion Starter · #104 · (Edited)
Next test is to wire the relay coil to the caps and the contacts still wired as the switch. As the caps 'cry' down to below 6V the the relay would open, turning off the switch. Resuming power to the cap circuit should close the relay turning the switch back on??? Sounds good on paper, real test will be next time at the bench. Open to all thoughts and suggestions.
EDIT: that will not work either, the relay coil will ultimately drain down the caps, unless the cap circuit is opened as well?????????? Still scheming.
Yes, this is the way I had intended. The cap holds the relay open while it powers the board until both the board and relay drain the cap enough for it to cut out. This is why we use such a low draw relay. No, don't expect 75 seconds.., more like 30+ seconds of idle time because current is lost to the relay as well as the board.

This is also why I put the diode between the cap and the B/B so that the caps' available current doesn't also backfeed and drain through that B/B board. I don't know that it would, but this is insurance that may not be necessary and actually is detremental in that it lowers the available voltage charge to the cap a bit. But..., you can always turn up the B/B by ~0.7 volt to compensate for the loss through the diode.
 

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toddalin, The board actually times out and turns itself off after 75 seconds of 0 track power, can actually hear the 'engine' winding down. The caps still shows over 6V, if I were to shut off the switch the caps stay charged and the system starts right back up when turned back on.
Second Thought: while I'd like more, 30 seconds may be long enough. And just applying power will turn it back on. Back to the bench, still scheming.
 

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While I should be satisfied with the operation of the existing circuit, and turn the unit off with the switch, I would like to take it one step further. Using the output of the limiter, which immediately drops to 0 when loosing track power, I would like to add a timer circuit, that is isolated from the caps that are feeding the sound board to prevent back feed. Would like to use one of the 6V relays I have, and I read where I could use the caps in parallel with the coil windings to slow relay from releasing, but have had no success so far. If I could get that to work would use the contacts in that relay to turn the board off AFTER about 60 seconds so the caps would still have some charge for the next time. Your thoughts please?? As a side note I found in the Sierra manual that there is an option for the board to turn off at 60 seconds OR only throught the switch. The option is already set for the 60 second setting, but is really 75, give or take.
 

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Discussion Starter · #107 ·
Yes, a cap will hold the relay open for a duration. I think the problem you are having is that the way the circuit is set up, the cap is acting to allow the armature to complete its motion and this is happening before the caps can take a full charge.

Did you try changing the 10 mfd cap for a larger value (e.g., 100 mfd)? A larger cap should take longer to the relay to pull in the armature, but should hold it there longer. But it could also be that the cap that is holding the relay open is also going to the Sierra so you are loosing charge there. If that's the case/in any case, I have another idea that would use a second relay.
 

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The circuits I attempted were totally separate from the Sierra battery replacement (post #82) circuit board. I tried using the 10UF and just didn't hold the relay up once the power was dropped, although I'm sure there should have been more to it than just the relay and cap. Don't have any 100UF, but may order some to test. (wish Radio Shack still had stores). Also noticed the relays come up at 3V, which isn't so bad either. Would like to see any ideas you have, thank you.
 

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Discussion Starter · #109 ·
I've been working (semi-retired consultant). Give me a little time to come up with something. It may be a matter of just using a diode to keep the relay cap from loosing its charge to the board with the Supercap.
 

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toddalin, I am hoping it to be a separate part not necessarily having interface with the battery replacement portion. This part will just be to replace the ON/OFF switch of the Sierra system. Just battery to the relay, possibly coming from the regulator but also isolated some how, with a cap as you described and a pot to be able to adjust the fall rate of the relay. Hope that makes the design much easier. I do appreciate your attention to this as I am enjoying what I call 'playing' with it. When we do get it working, I would hope you would publish the findings as you described in a previous posting. I'm just in it for the adventure, and I do thank you for your time and sharing your expertise. BTW, I did replace the 4 diodes I made the rectifier out of with a commercially made full wave rectifier. Trying to keep the power loss low went with one rated at 2A. After several hours of testing, attached a heat sink to the unit, so coming to the conclusion that a 3A unit would have been better as your original print suggested. As soon as you post I will order the parts needed.
 

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Catch Up: I did remove the resistor and diode between BB1 and the caps and as previously mentioned used separate boards for Boost and Limiter. Two days ago I energized the board with the locomotive on rollers and ran it successfully for several minutes. I also tested the quick raise in track voltage to activate the horn and it works also. After the run I reduced the track voltage to 0 and let it sit for 60 seconds before using the switch turned it off. The unit sat for two days and this morning I moved the switch to the ON position and the sound started immediately. Applied track power and all is well.
Observations: The 2A bridge rectifier got warm during the initial start up when the system was drawing in excess of 3A, but once everything got charged the amps dropped to a very acceptable level and the rectifier cooled. Am still going to replace it with a higher rated unit. I also noted when there is track power and the system is running, turning the switch to the off position does nothing until the track power goes to 0 then it shuts right off, and I believe the caps will still hold the charge.
Still playing with the ability to use the 6V relay contacts as the on/off switch, no success at this time.
 

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Discussion Starter · #112 ·
As I said, when the cap first charges, the circuit sees it as a dead short for a moment. That's why we put in the 4 ohm, 10 watt resistor. The short now becomes a minimum of 4 ohms, for a moment.

Using a value of 7 volts, this is 12.25 watts ((7 x 7) / 4), but for just a moment.

12.25 watts / 4 ohms = 3.1 amps, but for just a moment.

This is how I determined what values to use.
 

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toddalin: I now understand the reason for R1 (as I said, not trained in design only trouble shoot and follow schematics) and will add that to the circuit, thank you for explaining. That will take the load off the start up and probably will stop the heating of the rectifier, so will leave the 2A unit in place, for now. Will order the 4 ohm resistors. Do you have any advice on the cap size to slow down the release of the 6V relay so I can order several things at the same time and not incur shipping on each piece? You previously mentioned a 100mfd cap, do you still feel that will do it, and would a potentiometer be needed to fine tune it? Thank You Very Much
 

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Discussion Starter · #114 ·
Let me get a noise study for the City of Anaheim Public Utilities Commission out of the way today/tomorrow and I will look into it and do a schematic later this week. I'll go back over the thread to see what is necessary.
 

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Interesting observation: I ran several times, each time allowing the system to run different times, at 0 track power, before shutting off. The more the caps were discharged the higher the amps on the next start up. If the system is allowed to run 60 seconds or less the rectifier doesn't heat as much. Having said that, I did order the 4ohm resistors and will add one to the existing board and include it in the ones for my other loco's.
 

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When fully discharged, the caps are like a dead short. As charge is stored, the current flow slows down. Todds suggestion of an inrush resistor to limit current flow is how it is done.

You are definitely putting your 2 amp diodes at risk.

Have you ever monitored current when charging batteries? Same thing.

Greg
 

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Discussion Starter · #118 · (Edited)
If I'm not mistaken, I think this is what you want to do.

I think I have one of the relays so I can determine the value of C3 through experimentation. This will break the circuit between the wheels and Sierra Input as well as the supercaps and the "battery jack" when power is removed from the track after C3 discharges through the relay. The relay is actually a DPDT, and I've split the two sets of contacts in the schematic for ease of drawing/visualization. P1 sets the time the relay stays open. R2 ensures that when you turn the pot to the minimum value, you do not cause a short across the relay.

If this is what you think you want to accomplish, I'll play with the components to determine the value of the C3.

 

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Discussion Starter · #119 ·
OK, I did some testing and 24,000 mfd (a big cap) will hold teh relay open for ~15 seconds, so figure a minute is about 100,000 mfd. That's a BIG cap, unless you use supercaps. In which case C3 is three supercaps together, just like C2, and put a 4 ohm, 10 watt resistor between BB1 and D2 to reduce the inrush.

And these supercaps can be smaller in Farads if desired. The three 6F caps (2 F), will hold the relay open for lots of minutes. I got tired of waiting after over 3 minutes so the board would time out time after time if the pot were not there to let this "bleed down" quicker.

There is also a way to use the three existing supercaps and I'll do the schematic next.
 

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Discussion Starter · #120 · (Edited)
I fixed the last schematic to include the second set of supercaps. These don't need to be as big. We double R1's value so as not to overtax the B/B, bridge, etc. with the addition of the second set.












 
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