need some help guys

[kidkv]

<snip>

When you say "8.50v out thats on and off", what exactly do you mean?
(You need to describe things more clearly)
Do you mean that a measurement from ground to the collector of Q205
shows 8.5V whether or not it's turned on? ie With the output of U201C low
and 0V at the base of Q205, the collector measures 8.5V and with the output
of U201C high, the collector is still at 8.5V and the base is at 0.7V?
The part about a jumper from collector to emitter loses me. How would
that turn the transistor on? Or did you mean that the relay would turn on?

Again, I have to re-iterate that you have to describe things more
accurately if you want help.

... Johnny

this is true
With the output of U201C low

and 0V at the base of Q205, the collector measures 8.5V and with the output
of U201C high, the collector is still at 8.5V and the base is at 0.7V?

a jumper from collector to to emitter or gnd would kick the relay on
then it would stay on for some time and then after maybe 2 to 5 mins
the relay would drop out. it's like the darlington's are on for some
time when i do that.
i have only one 5v trace on the board???? i know that i have 5volts
from the power supply but at the last chip i get 4.50v
darlington's are npn

does this help out more?????

 

[Johnny Boy]

this is true
With the output of U201C low

a jumper from collector to to emitter or gnd would kick the relay on
then it would stay on for some time and then after maybe 2 to 5 mins
the relay would drop out. it's like the darlington's are on for some
time when i do that.
i have only one 5v trace on the board???? i know that i have 5volts
from the power supply but at the last chip i get 4.50v
darlington's are npn

does this help out more?????

Something doesn't sound right. I'd try another Darlington, for starters.
Also double-check all connections for open-circuits or shorts.

What's this about the 5V supply? You keep adding new problems. Now, you
have the Darlington problem and the frequency counter problem and yet
another problem with the 5V supply? I you're experiencing a drop in the 5V
rail, trace back to the point where it drops from 5V to the lower 4.5V and
see what you can find.

.... Johnny

 

[kidkv]

Something doesn't sound right. I'd try another Darlington, for starters.
Also double-check all connections for open-circuits or shorts.

What's this about the 5V supply? You keep adding new problems. Now, you
have the Darlington problem and the frequency counter problem and yet
another problem with the 5V supply? I you're experiencing a drop in the 5V
rail, trace back to the point where it drops from 5V to the lower 4.5V and
see what you can find.

... Johnny

i did try new darlingtons but the relays will not turn on:-( if i can
get the relays to turn on i can hook it up to the welder to use it. the
frequency counter problem i can trace to 74hct112
if i take a jumper wire from gnd to pins15,14 rst it will stop the
counter but not in the 50hz to 400hz it will stop from 000 to 999. i
may look at a new frequency counter circuit...

steven

 

[Johnny Boy]

i did try new darlingtons but the relays will not turn on:-( if i can
get the relays to turn on i can hook it up to the welder to use it. the
frequency counter problem i can trace to 74hct112
if i take a jumper wire from gnd to pins15,14 rst it will stop the
counter but not in the 50hz to 400hz it will stop from 000 to 999. i
may look at a new frequency counter circuit...

steven

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

 

[kidkv]

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

 

[xray]

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.

 

[Johnny Boy]

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.

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

 

[kidkv]

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

 

[Johnny Boy]

ok will do some testing tonight
steven

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

 

[kidkv]

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

 

[kidkv]

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

 

[Johnny Boy]

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

 

[kidkv]

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

 

[xray]

google

You mean GooTube?

 

[kidkv]

You mean GooTube?

yea gives you 1,000,000+ things that you don't whant on just one
thing......

steven