At this point I don't know what to suggest. If all connections are as shown on the schematic, then when the output of U201C goes high, Q205 should turn on, energising the relay. If I were you, I'd go over all connections and double-check that the transistors are in the right way around, etc. Something is wrong. Of course, with only 18V supply for the relays, they might not turn on, due to the extra voltage lost across the transistor's collector/emitter.
... Johnny
ok i will look at the boards agian and if i find all is ok i will see if i have a 24v trans if not i will use two 12v trans thanks for the help johnny and all
steven
Just measuring the voltage across the output of the switch darlingtons in the on and off state (or the voltage across the relay) should tell you a lot about whether the switching is working at all. I wouldn't change the relay supply until I proved that it is really necessary and you don't have some other problem.
on,
collector/emitter.
I agree wholeheartedly. There most certainly is some other problem there. I didn't mean to imply that the low supply voltage could cause this problem. The OP's measurements across the Darlingtons shows that either the connections are wrong or the Darlingtons are blown.
... Johnny
ok will do some testing tonight steven
turn
there. I
problem.
Good one Steven, I didn't want you to (incorrectly) think that increasing the 18V power supply would cure your problem. Chances are that you have a few problems in this circuit that will need correcting. I wish I could help you more - I remember what it's like to be starting out and trying to understand this stuff. On the positive side, although this is probably getting you down a bit, I'm sure that you've learned heaps in the process. That's what's important. Overall, though, your problems appear relatively simple. I wish I was there with my DMM to help solve this more quickly. I'd say that a few quick measurements would sort things out. Where are you, by the way? I'm in Nowra, NSW, Australia. I assume that you're a long way from here. After you do your tests, post the results and maybe one of us can help further. ... Johnny
hey i found what was wrong the darlingtons whear in backwards the e was at the b ::-0 that fixed the relays now they turn on like they should... EAGLE had the wrong pin out on the darlingtons.. i am in the U.S state P.A now just have to get the freq counter to work. but now i can use it..
thanks for the help Steven
It just shows that you should look over the datasheets to see it the pins are right ?????????
steven
Well done - I knew it had to be something like that. And yes, it's always a good idea to check the datasheets when you strike a problem. The frequency counter might be trickier. I'll take a look and see if I can think of anything.
... Johnny
ok and this is true "On the positive side, although this is probably getting you down a bit, I'm sure that you've learned heaps in the process. That's what's important." i did simple stuff at first and have learned a lot more as i move on up... when i can't get help i try to use google as much as i can and it has helped out alot.
steven
You mean GooTube?
yea gives you 1,000,000+ things that you don't whant on just one thing......
steven
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