strantor, your design will work if you just put a pull-down resistor on the base of the pnp and the nightwatchman is very close to the supply voltage when its output is high. If the output isn't all that high, we can use a zener for a "spacer". 560 ohms to get 20 ma drive on the base and 200 ma on the collector (as a saturated switch).

Ifly: Nothing is set in stone..yet. Go get a couple of 5 pin car relays (single pole, double throw). Hint: There are dead cars in the junk yard. If not convenient, pay retail.

For the limit switches, 3 pin microswitches (single pole, double throw) are pretty common and cover what we need. Right strantor?

Edit: Alarm! If you tried to measure continuity of the nightwatchman (from output to ground) when it was in the "night" condition, it applied 12 volts to your ohm meter. Check for a blown fuse.

 

I'll pick up the relays and let you know exactly what they are and their specs (probably this evening). I have the limit switches you are talking about. I use them by the handfull in my larger aircraft. Anything else I should be able to get at the local Radio Shack on monday, and if not, from online. The tester is fine, I knew it would do that and checked night mode without power applied. Todd

 

I cleaned up strantor's drawing and got most of it correct.

 

OK, I had to wait till today to get to a couple of the other auto stores. In a nutshell, I ordered 2 Bosch type 961A-1C-12DM 30/40 amp relays online; out of 5 different stores, none had more than one of anything. I also ordered 2 relay sockets; all this with the shipping cost about the same as one relay from any of the stores and will only be a day or 2 later to be in my possession. Other than the limit switches which I already have, what would I need to get from radioshack to finish the shopping list off. Todd

 

I need measurements. We have done as much as we can without measurements.

I need the current the relays use.
I need the voltage difference across the nightwatchman while it is activating a relay coil.

See post #17.

When you get done with that, I can finish the design.

 

Ok, it's going to be a few days till they come in and I'll get the actual measurements you need as to one of your earlier posts. Here are the specs for the relays as to the manufacturer:

Rating load current : 40A, 12VDC
Coil voltage : 12V ( 7.2V start )
Coil current : 133mA, typical
Coil resistance : 90ohm, typical
Contact type : 1C, SPDT
Contact resistance : <=50mohm
Max switching voltage : 12VDC
Max switching power : 480W
Operating temperature : -40~+85C
​

I'll get you the actual measurements once they come in; thank you so very much for the help!!! Todd

 

This stuff has to be measured because we are using the "nightwatchman" outside its design criteria. The answers will not be provided on THAT datasheet. Meanwhile, it's good to have the numbers for the relays. Thank you.

 

Bump.

Expecting an answer from OP. Trying to keep this where he can easily find it.

 

12, are you talking to me or someone else? If me, I won't be able to get the measurments for you till late this week at the soonest. The relays have a deliver date of the 11th by FedEx and I bet they won't actually get here till Monday; hope I'm wrong and they get here by the end of the week. Todd

 

I guess you'll have to go poking around in the old pages to find this...or put a "bookmark" or "favorite" tag on it, right now.

That way, I won't have to babysit it.

 

I get notified by email with a link to the thread whenever anyone posts anything to it. I can go directly to it.

 

That will work.

 

Ok #12, the package was waiting for me when I got home this morning. I hooked everything up the way you were wanting for the specific measurements,... I hope. First the resistance through the coil with the ohm meter set at 200 the reading was 11.9 and when set at 2K it was .012. The initial numbers on the display when not hooked to anything was 13.7 and .013 respectively.
When testing for "sink" the relay did not activate and the only reaction was for the to light the diode stating that a circuit was activated.
I attached the relay to the night watchman as a load, connected the night watchman and the relay to ground, and covered the eye; the voltage dropped from 12.14 to 12.08. With everything still hooked up, I measured across the coil and got a reading of 12.07.
I hope I got the numbers you want and need and that I did them correctly. Let me know when I may do anything else. Thanks, Todd

 

Just a detail. With a relay coil hooked up as a load on the nightwatchman, I need the voltage loss from the INPUT of the nightwatchman to the OUTPUT (where the relay is attached as a load). That's in case the 13.7 volts is not still 13.7 when the nightwatchman is powering a relay. The 13.7 volts doesn't matter exactly. This circuit will work at 16 volts, 15 volts, 14 volts, 13 volts, or 12 volts. In order to get the measurement I need, I need to know how much voltage gets lost inside the nightwatchman when it's powering a relay. The answer will be anywhere from zero to a volt or 2. I need a good measurement...within a tenth of a volt of accuracy.

Your ohm readings are off by a power of ten. They should be about 90 or 100, not 11 or 12. Read the labels on the meter carefully to be sure you are on the right scale. Still, this is not important now that you have posted the specs on the relay.

 

Alright, with the night watchman positive hooked to a battery, the ground from the night watchman and one side of the coil hooked to the negative of the battery, and the load line from the night watchman hooked to the positive (other side) of the coil, the voltage when the negative probe is connected to the ground and the red touched to the positive input to the night watchman/battery + is 12.14. Moving the positive probe to the load side of the night watchman the meter reads nothing in daylight mode and when activated for night mode goes to 12.12V - a drop of .02 volts.
I looked at my meter again (it's an older sears craftsman digital + analog multimeter #82320); the ohm range goes from 200, 2k,20k,200k,2M,and 20M ohms. With nothing hooked up to it, the 200 range reads 13.7 and the 2k reads .013. When the meter was hooked up to the circuit as before, it read 11.9 and .012 respectively. Is my meter not reading correctly?

 

With a relay coil hooked up as a load on the nightwatchman, I need the voltage loss from the INPUT of the nightwatchman to the OUTPUT (where the relay is attached as a load).

Not from the input to ground. Not from the output to ground. From the input to the output while it is powering a relay.

and yes, your ohm meter is not making sense.

 

That measurement reads 0.

 

Thanks. I started out trying to do this with Radio Shack but they have so little stock!
I'm gonna have to put you in the position of ordering through the mail (or paying outrageous prices at Radio Shack) unless you have a local electronics store.

Do you have a local electronics store? Are you perfectly willing to order online?

and what about a piece of pad-per-hole perfboard to make the transistorized part with? A cute little box to protect it from the weather and chicken poop? Big enough to house the relays, too? or are they waterproof?

I'd replace the zener diodes with MOV's if it was convenient to order online. It lowers the parts count (and the price)to do that.

or is this enough that you can run with it from here?

Talk to me...

 

As far as I know, Radio Shack is the only electronics store around here. I have absolutely no problem ordering off the net. All parts of this project are safe indoors and only need to be protected from the chickens and dust. I can make any enclosure or come up with one. I would need to come up with the circuit board and I know that the local RS has them. I'll get or order anything that you tell me I need; do you have a personal favorite website that you order from? All I need is a shopping list and I'll make it happen. If I can get a wiring diagram with all the individual parts on it I think I can figure it out; if not, I'll be giving you a shout for a little more help. Todd

 

My fav is www.mouser.com but there is also digikey, Jameco, and half a dozen others.
I'll get to work on this now. Much prefer 19 cent MOVs to $1.20 at Radio Shack! The base price for shipping is about $10.50 but you save that much (compared to RS) by the time you order 10 or so parts.