Walk Test LED

kmitch

Well-known member
Joined
Dec 11, 2001
Messages
429
Reaction score
0
I finally was able to breadboard the internal timer mods tonight. One observation is that the time delay will become shorter as the battery voltage decreases. I was able to get it to operate at 12, 9 and 5 volts. In the 6v setup I was able to get it to operate at 4.5 volts. With the timer set for 2 minutes at 6v it decreases to about 1 min 30 seconds at 4.5 volts.

Has anyone figured out how to make the walk test LED work with the internal timer mod? Previously it was connected to pin 14 of the LM324 and the switch was left in the TEST position. I  used a DPDT switch, one side switches the LED, the other interrupts the output to the camera.

With the timer mod the TEST/NORMAL switch must be in the NORMAL position for the mod to work. Then pin 14 operates with the time delay.

One
 



ArkansasElkHunter

Well-known member
Joined
Jan 19, 2002
Messages
1,748
Reaction score
0
Kmitch,

You can add a spdt and switch between supplying power to the coil on the relay and the led.  That will work.  I'm not sure if there will be a "single Switch" method to do it and have a short time delay for testing.  

You will either have to use pin14 and flip the slide to test mode, leaving the camera off (just let the relay do its thing)or use a toggle to switch between the relay and led, and also reduce the delay time to 2 sec or so.

If the Mode Slide switch has a ground side you might use that to ground your led and get power for the led from pin 14.  I don't know what will happen if you try that.  Just might be and idea to try.  

Having a fast test time will be esential to the camera mods,  you can get that but it would be nice to only flip one switch.  Someone here will be able to figure this one out.
 

Jon5ja

Well-known member
Joined
Jun 6, 2002
Messages
722
Reaction score
0
kmitch,

My intent was to leave the TEST position functional as it was before.  Unless I'm missing something, when the TEST/NORM switch is in the TEST position, the added circuitry is basically bypassed, so you should have short-duration, un-inhibited testing.

Or, were you using the TEST/NORM switch to switch between the camera and the LED?  Or as separate switch?

By the way, the 15K resistor shown in the timer schematic should really have been increased to 330K ... the 15K was left-over from before I replaced R27 with a 100K.  It won't hurt anything to leave it 15K, it'll just draw more power when activated.

Jon

(Edited by Jon5ja at 1:47 pm on June 20, 2002)
 

ArkansasElkHunter

Well-known member
Joined
Jan 19, 2002
Messages
1,748
Reaction score
0
Jon,

We would normally just disable the led and enable the camera to switch between test and picture mode.  the test/normal slide switch was only to change to the longer time delay built in.  What we need is a simple single switch  from test mode to picture mode
 

kmitch

Well-known member
Joined
Dec 11, 2001
Messages
429
Reaction score
0
AEH is right. I use a DPDT switch which is accessible from outside the cam case to switch from TEST to ARM. In the TEST position, the LED circuit is enabled and the Camera shutter is disabled. Vice versa for the ARM position, the camera shutter is enabled and the LED is disabled. These are two different circuits so they are on opposite sides of the DPDT. I much perfer to have this switch outside the cam enclosure. The last thing I do before I leave a setup is do the walk test. Since I use ammo cans for enclosures I don't want to disturb the setup when I close the can.

I can make it work with the TEST/NORMAL switch on the MS20 by going to the TEST position and unplugging the camera.

One thing I considered is replacing the DPDT switch in the MS20 with a toggle switch mounted through the cam case. Would still need to interrupt the relay output to the camera to make it work.

I'm going to play with some ideas tonight.

Then again, maybe we can't have it all. With Jon's help we've jumped light years ahead in just the last few weeks.

Keith
 

kmitch

Well-known member
Joined
Dec 11, 2001
Messages
429
Reaction score
0
Think I figured out the walk test switch. Here's the schematic Use a DPDT switch. Break the connection between pin 14 and R28 and insert one part of the switch as shown. Use the other part of the switch to shunt the timing pot and cap with a 5.1K resistor to reduce the timing value. 5K gives about a 5 sec on time with a 6v supply.

Keith
 

Jon5ja

Well-known member
Joined
Jun 6, 2002
Messages
722
Reaction score
0
Keith,

What you did should work.  The only negative is that, since you're running in NORMAL mode, you'll have to wait 10 seconds or so for the timer to drop out.  You can save yourself a resistor by shorting the base of Q3 to ground (it's hooked to the top of JP1A, clipped out of the picture below) instead of messing with the timer circuit.  Using a 3PDT switch, you could do this:



If you don't mind the 10 seconds or whatever, you can eliminate the "B" section and just use a DPDT switch.

I also tried using diodes -- I'll just describe it instead of drawing it -- I didn't cut the path of R28, I just connected the anode of a 1N4148 to the base of Q3 (top of JP1A), another to the switch end of R26 (top of JP1B), another to the base of Q4, and the LED resistor to pin 14, the other end to the anode of the LED.  I then connected the cathodes of the three 1N4148's and the LED together, and hooked them to an SPST switch with the other side of the SPST going to ground.  When the switch was closed, it kept Q3 turned off, Q4 turned off, put R26 in the circuit, and grounded the LED so it'd come on, and you'd be in WALK mode.

This actually worked!  :)  I wouldn't advertise it, though, because the forward voltage drop of the 1N4148's is very close to the B-E junction voltage of the transistors I'm trying to shut off, and it might not always work if you duplicated it.  However, if you used Schottky diodes like BAT46's or something instead of 1N4148's, you could be confident it'd work.

Cheers,
Jon
 

kmitch

Well-known member
Joined
Dec 11, 2001
Messages
429
Reaction score
0
I woke up this morning and realized that although what I posted last night will work it doesn't work the way I had thought. I have another idea. If it works I'll put up something tonight. In the mean time I'm going to vaporize the schematic.

Keith
 

Latest Posts



Top Bottom