G Scale Model Train Forum banner
121 - 138 of 138 Posts

·
Premium Member
Joined
·
2,044 Posts
toddalin: first thank you very much for taking the time to do this, and timed relay release operation is exactly what I am looking for. My only concern is you mention with C3 at 1F will give the relay 3 minutes of open. That is much too long as the board shuts down at 75 seconds and the Sierra stutters at the next start up.. Can P1 be adjusted down to about 60 seconds? or do other changes need to be made to accomplish that? Much appreciated.
 

·
Registered
Joined
·
3,522 Posts
Discussion Starter · #122 · (Edited)
By my estimate, P1 can turn it down to ~30 seconds. Ideally, we would want to find supercaps (C3) with a value of about 0.5 farad which would take this down to about 15 seconds minimum and 1-1/2 minute max.

This can also be adjusted by decreasing the value of R2. Instead of 100 ohms, 50 ohms reduces the minimum time by ~half, but you would want to increase the value of the resistor to 1 watt.
 

·
Registered
Joined
·
3,522 Posts
Discussion Starter · #123 ·

·
Premium Member
Joined
·
2,044 Posts
toddalin: 15 - 90 seconds is great and allow for minor variances in mass produced components, track and locomotive variables and personal preferences. While waiting I was doing more playing:
For my first conversion I am using an Aristocraft FA locomotive set. The motors on these units start the wheels rolling at 4 volts at the track, same as the boost board coming into effect. To give myself a small window of operation I added diodes to drop the track voltage to the trucks. The wheels now start to move at 5.5V. I will have to change Set Up Step 1: Start Voltage setting on the Sierra board to correspond with the new movement.
toddalin, thank you again for taking the time and your expertise helping us revive what is a good and still usable sound system. Creating a shopping list and will post your SUCCESS in a couple of weeks.
 

·
Premium Member
Joined
·
2,044 Posts
toddalin, thank you for the update, modifying shopping list which also changes source of some items. The pots I had on the list were only good for 250mw, the variable resistors are good for 5w. Still havin' fun.
 

·
Registered
Joined
·
3,522 Posts
Discussion Starter · #128 ·
After you have it up and running, with your selected voltage from the B/B, take a voltage reading across the relay. The inline diode will reduce this a bit (~0.7 volt). If you find it is over ~6.5 volts, put a 1 amp diode in series with the relay to reduce its voltage by about 0.7 volt and make it easier on the relay's life span. This will also reduce the timing a bit because the relay will kick out a lower voltage due to this voltage reduction.
 

·
Premium Member
Joined
·
2,044 Posts
toddalin: will print the above and save it, along with all your other postings on this topic. It will be a couple of weeks before I have all the components for the timing relay.
Made another board, this time I have the 4ohm resistors, which I will add another in series or replace with an 8 when I add the timing board. Can see the difference on the meters. The initial surge is reduced and takes a bit longer for the caps to reach the output value of the regulator, which isn't noticed as the system is generating sound while the caps are charging.
 

·
Premium Member
Joined
·
2,044 Posts
toddling: did some playing with the relays I have, exact part number you advised. Found they go off normal at 2.5VDC, is that how you figured the release circuit and timing? Thank You
 

·
Registered
Joined
·
3,522 Posts
Discussion Starter · #131 · (Edited)
No, I simply took a relay and charged up a ~24,000 mfd cap, and timed how long it stayed open, about 15-16 seconds.

From there you can calculate timing value as a fairly linear relationship, (i.e., 100,000 mfd ~ 1 minute)

0.5F = 500,000 mfd

1/((1/0.5)+(1/0.5)+ (1/0.5)) = 0.1667F

166,667F/100,000F = 1.6667 x 1 min = 1.6667 min x 60sec/min = 100 seconds (give or take)

IIRC, the relay is listed at 80 mA at 6 volt or ~450 ohms

1/((1/450) + (1/10,000)) = 430 ohms

430 ohm/450 ohms x 100 sec = ~95 sec. max time

Turn pot to min:

1/((1/450) + (1/100)) = 82 ohms

82 / 450 x 100 = ~18 sec
 

·
Registered
Joined
·
3,522 Posts
Discussion Starter · #132 ·
BTW, I would urge you to also perform this experiment.

You have the relays. Just take a big capacitor of known value and charge it up to the voltage that C3 would be expected to see (after the B/B and big diode), disconnect it from the power source, put it across the relay leads, and you will hear the relay click closed. Time how long it takes to click open.

From there, the timing is a ~linear relationship based on the size of from the cap (mfd) and the resistance (ohm) across it.

You can also see what it does to the timing if you put a diode between the cap and relay as this will knock down the voltage a bit.
 

·
Premium Member
Joined
·
2,044 Posts
toddling, I did just what you described, several days ago, with the super caps and resistors I have on hand. I wouldn't be able to hear the relay operate, but did use a meter across the make contacts so I could see it. The best I was able to come up with, using the caps I have, and by adding resistors took over an hour for the caps to discharge to the point the relay released. I was headed in the right direction, but the answer was out of my grasp, I ran out of options. Being able to calculate the needed values permits you to go directly to the answer, I don't have that ability so have to keep adding or removing components to get to where I want to be, and that doesn't always work. Again thank you for your time and expertise.
 

·
Premium Member
Joined
·
2,044 Posts
I didn't abandon the project, it took a while to receive all the components for the time out circuit. I tested using power from a transformer and an ohm meter to watch the contacts.
A BEAUTIFUL SIGHT. Variable resistor came from factory set in the center, measured 5K ohms. The input voltage also effects the relay hold time. Using 6V the hold time was 45 sec, 7V was 60 sec. So between the input voltage and the variable resistor there should be a very wide range of cut off timing. Interfacing the two boards is a simple matter of picking up power from the limiter output and using the NO contacts in place of the I/O switch. Before I do that I want to play some more. I'm sure this has helped many of us make use of existing if outdated sound systems. Toddalin, great engineering and design and once again THANK YOU VERY MUCH. I had fun and the outcome is very rewarding.
EDIT: left is the timing circuit, right is the battery replacement board.
 

Attachments

·
Premium Member
Joined
·
2,044 Posts
Made another timing board this morning, with a wiring error, easy fix. Cataract surgery '21 days and a wake up', can't come soon enough.
 

·
Premium Member
Joined
·
2,044 Posts
Playing: using 7V input, after the initial charge takes minimum 60 sec to get a full charge, longer had no effect but shorter lessened the time out. Using the uxcel Variable Resistors 10K ohm 5W from Ebay. (ref the pic) from factory A-B is 55K, B-C50k, pretty close to the 60 sec I wanted. Found 2 revolution of the adjustment screw changed the release time by 4 seconds, up or down depending on which connections you used and what direction you turned the screw.
B-C CCW raised, CW lowered resistance----- A-B CCW lowered, CW raised. Hope that makes it easier for those doing this. 19 days and a wake up.
 

Attachments

·
Premium Member
Joined
·
2,044 Posts
As I mentioned I advanced the Super Cap circuit to the Sierra board using the existing battery leads, leaving the I/O switch as ONE way to turn it off.. Using this option gives an instant start as long as the switch goes OFF within the 90 seconds of full discharge. Second option using the timing circuit. This caused the sound board to give a very short grunt while the caps on the timeout board charged. Either way is totally acceptable. This will be my last posting on this subject. Toddalin, again thank you very much for your time and expertese. I will continue to play with these circuits and convert my other Sierra's to this system.
 
121 - 138 of 138 Posts
Top