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need some help guys

K

kidkv

Jan 1, 1970
0
can you look at this circuit and tell me if the caps CP202 and CP203
are right
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/TIGTIMING.pdf
and can you tell me why i am geting 0.71volts to Q205 and Q206 when the
2n3904 is geting 5volts
and if i put a lower ohm resistor to give more voltage the voltage from
the 74hct14 gos from 5 volts on the output down to 2 to 1 volts this is
what i can't get.....
 
K

kidkv

Jan 1, 1970
0
kidkv said:
can you look at this circuit and tell me if the caps CP202 and CP203
are right
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/TIGTIMING.pdf
and can you tell me why i am geting 0.71volts to Q205 and Q206 when the
2n3904 is geting 5volts
and if i put a lower ohm resistor to give more voltage the voltage from
the 74hct14 gos from 5 volts on the output down to 2 to 1 volts this is
what i can't get.....
come on someone has to know something
 
E

Eeyore

Jan 1, 1970
0
kidkv said:
come on someone has to know something

How is anyone supposed to guess at your cap values ?

More info pls !

Graham
 
K

kidkv

Jan 1, 1970
0
Eeyore said:
How is anyone supposed to guess at your cap values ?

More info pls !

Graham
the caps are 10uf and i need to know if electrolytic will work like
that to turn on and turn off that relay and i can't get why the voltage
drops down on the 74hct14 chip when i put a lower
ohm resistor to give more voltage the voltage go's down the resistors
are r226,r227 they are 4.7k and i get .71 volts out on it and the
voltage going in is 5 volts????
 
J

Johnny Boy

Jan 1, 1970
0
kidkv said:
can you look at this circuit and tell me if the caps CP202 and CP203
are right
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/TIGTIMING.pdf
and can you tell me why i am geting 0.71volts to Q205 and Q206 when the
2n3904 is geting 5volts
and if i put a lower ohm resistor to give more voltage the voltage from
the 74hct14 gos from 5 volts on the output down to 2 to 1 volts this is
what i can't get.....

Q205 and Q206 are Darlingtons, (the type isn't mentioned), so I would
have thought that the base voltages would have been a little higher, in the
neighbourhood of 1.2V on each, rather than 0.71V. Are you measuring the
collector voltage by mistake instead of the base voltage?
As for the 2N3904, if you're measuring 5V at the base, then something is
wrong. (Maybe the emitter's ground connection is OC.) Are you sure you're
measuring the base voltage, or on the other side of the series base
resistor?
The caps would work to turn on the relay for a short period determined
by the cap/resistor values. (A crude timer) The time period would be in the
neighbourhood of 0.1S.

.... Johnny
 
P

Paul E. Schoen

Jan 1, 1970
0
kidkv said:
the caps are 10uf and i need to know if electrolytic will work like
that to turn on and turn off that relay and i can't get why the voltage
drops down on the 74hct14 chip when i put a lower
ohm resistor to give more voltage the voltage go's down the resistors
are r226,r227 they are 4.7k and i get .71 volts out on it and the
voltage going in is 5 volts????

For one thing, there is no pullup on U201A and U201F, so they may act
erratic or oscillate. The circuitry for the off-page connections such as
END_C_ON is not shown, so they may be affecting the operation. Also, the
unused op-amps and comparator gates should not have both inputs tied to the
same potential, as this may cause oscillations. Tie the output to the
inverting input. If you are using CP202 and CP203 to produce a timed pulse,
it would be better to use your unused op-amps for a better-defined pulse.

Better yet: implement the whole circuit with a PIC!

Paul
 
K

kidkv

Jan 1, 1970
0
Johnny said:
Q205 and Q206 are Darlingtons, (the type isn't mentioned), so I would
have thought that the base voltages would have been a little higher, in the
neighbourhood of 1.2V on each, rather than 0.71V. Are you measuring the
collector voltage by mistake instead of the base voltage?
As for the 2N3904, if you're measuring 5V at the base, then something is
wrong. (Maybe the emitter's ground connection is OC.) Are you sure you're
measuring the base voltage, or on the other side of the series base
resistor?
The caps would work to turn on the relay for a short period determined
by the cap/resistor values. (A crude timer) The time period would be in the
neighbourhood of 0.1S.

... Johnny

yes it is at the base the darlingtons are nte46 Base-Emitter ON
Voltage VBE(on) IC = 100mA, VCE = 5V - 1.4 2.0
the rest of the circuit works i just need to get the darlingtons to
turn on witch i can't get the voltage up to turn them on from what i
got it would be a 15ohm resistor to get 1.5 v right ????

ther is more to the circuit
 
X

xray

Jan 1, 1970
0
yes it is at the base the darlingtons are nte46 Base-Emitter ON
Voltage VBE(on) IC = 100mA, VCE = 5V - 1.4 2.0
the rest of the circuit works i just need to get the darlingtons to
turn on witch i can't get the voltage up to turn them on from what i
got it would be a 15ohm resistor to get 1.5 v right ????

ther is more to the circuit

What makes you think they are not "on". What is connected at that K1
coil place. You do realize that a voltage won't come out of the
darlingtons, right? When "on" the transistor pulls the load to ground.

The base resistor is forward biasing the e-b junctions of the two
transistors in the darlington pair. The voltage at the base will be
whatever the two transistor diode drops in series are. As was already
mentioned, .71 V seems more like one diode drop than two. It is a bit
puzzling, but you seem to think you want the base to get to 5V. If it
does, it will only be after you release the smoke from the transistor.
 
J

Johnny Boy

Jan 1, 1970
0
kidkv said:
yes it is at the base the darlingtons are nte46 Base-Emitter ON
Voltage VBE(on) IC = 100mA, VCE = 5V - 1.4 2.0

1. Are you designing or repairing this? If you're designing it, it seems to
me that you need to study a little more transistor theory first.
2. What do these Darlington's drive? (The load should, of course, be
connected between the collector and a higher positive voltage.) If the
higher positive voltage is 5V and the Vce on is 1.4V, then you can only
drive a 2V load.
the rest of the circuit works i just need to get the darlingtons to
turn on witch i can't get the voltage up to turn them on from what i
got it would be a 15ohm resistor to get 1.5 v right ????

Why 15 ohms?
5V - 1.5V = 3.5V. 3.5V across a 15 ohm resistor is 233mA. A 74HCT14 can
only source or sink a maximum of 25mA per pin. That's why you can't get the
voltage to rise above 0.7V. You're trying to murder the 74HCT14.

If the collector current is 100mA, then even if you force 1/10 of that into
the base, (10mA), then the smallest resistor you would need is 350 ohms. In
reality, since these are Darlingtons, you need far less current and a larger
resistor value. (See 1. above)
ther is more to the circuit
Obviously. It would probably help if you showed us the whole thing.
.... Johnny
 
K

kidkv

Jan 1, 1970
0
Johnny said:
1. Are you designing or repairing this? If you're designing it, it seems to
me that you need to study a little more transistor theory first.
2. What do these Darlington's drive? (The load should, of course, be
connected between the collector and a higher positive voltage.) If the
higher positive voltage is 5V and the Vce on is 1.4V, then you can only
drive a 2V load.


Why 15 ohms?
5V - 1.5V = 3.5V. 3.5V across a 15 ohm resistor is 233mA. A 74HCT14 can
only source or sink a maximum of 25mA per pin. That's why you can't get the
voltage to rise above 0.7V. You're trying to murder the 74HCT14.

If the collector current is 100mA, then even if you force 1/10 of that into
the base, (10mA), then the smallest resistor you would need is 350 ohms. In
reality, since these are Darlingtons, you need far less current and a larger
resistor value. (See 1. above)

Obviously. It would probably help if you showed us the whole thing.
... Johnny

k1 go's to a relay. relays are 24vdc with 18.00 vdc powering them
hear is the rest of the ciruit
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/SYSTEMDRAWING.pdf
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/CONTROLPANEL.pdf
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/dbARC_START.pdf
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/FREQCOUNTER.pdf
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/TIGWELDERTOP.pdf
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/TIGPOWER.pdf
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/OUTPUT200A.pdf
 
J

Johnny Boy

Jan 1, 1970
0
kidkv said:
and one more that won't work is the freqcounter will not read the freq
it starts at 000 and ramps up to 999 and then starts over
i hope all of you can help me

steven
Are you repairing or building this thing? In other words, was it once
working, but now isn't, or has it never worked yet?
.... Johnny
 
K

kidkv

Jan 1, 1970
0
Johnny said:
Are you repairing or building this thing? In other words, was it once
working, but now isn't, or has it never worked yet?
... Johnny

i am building this from plans on line. the one that built it does have
it working i have sent emails to him and got the info on it and parts
that are not in the pdf files.. but right now he has tooo much work to
help he has been sick and was out for 3 weeks so that is why i came
hear... i know the basic circuits but i am geting in to cmos circuits
and did read up on them...

steven
 
J

Johnny Boy

Jan 1, 1970
0
kidkv said:
i am building this from plans on line. the one that built it does have
it working i have sent emails to him and got the info on it and parts
that are not in the pdf files.. but right now he has tooo much work to
help he has been sick and was out for 3 weeks so that is why i came
hear... i know the basic circuits but i am geting in to cmos circuits
and did read up on them...

steven

Does the relay turn on when Q205 is turned on?
Does the output of U201C go fully high, (5V), with the original 4K7 base
resistor, (R226), to Q205 in place? (When you say the Q205 base voltage is
0.71V?
Out of interest, are you making this on a pre-manufactured PCB, or using
other means?
.... Johnny
 
A

Ancient_Hacker

Jan 1, 1970
0
kidkv said:
can you look at this circuit and tell me if the caps CP202 and CP203
are right
http://www3.telus.net/public/a5a26316/WelderPDFs_Pics/TIGTIMING.pdf
and can you tell me why i am geting 0.71volts to Q205 and Q206 when the
2n3904 is geting 5volts
and if i put a lower ohm resistor to give more voltage the voltage from
the 74hct14 gos from 5 volts on the output down to 2 to 1 volts this is
what i can't get.....

Hate to say it, but this is a pretty crappy design:

(1) Using schmitt triggers as timing elements is not terribly keen--
the electrolytic capacitors tend to have wide variations in leakake and
capacitance. Also using monostables around BIG ELECTRICAL ARCS is not
very keen! They're likely to jitter all over the place. This type of
design really calls out for some digital timing.

(2) There are several boo-boos in the schematic, even at a quick
glance. One monostable doesnt have a pull-down resistor, unless it's
in the off-page link. Several of the coil drivers don't have
transient-clipping diodes or current-limiting resistors. The resistors
on the unused circuits are really bizarre. Feeding the unchained
comparator and even schmitt triggers from an off-page link is likely to
result in serious oscillations. I don't see any power supply bypassing
capacitors.

I'd give this circuit design a grade of about D+. It might just may
work under ideal conditions, but it's unlikely to work well and
precisely without some tweaking.

It reminds me of quite similar control board for a $3000 tape recorder.
Under low-humidity conditions, the audio tape would build up small
static charges-- you could hear them discharging to the metal guide
posts with a very faint "tick" sound. ABout 30% of the ticks caused
the control board to misfire, often sending the deck into stop, rewind,
fast-forward, or one or more all at the same time. I don't think you
want this to happen with things like gas valves!
 
A

Ancient_Hacker

Jan 1, 1970
0
kidkv said:
and one more that won't work is the freqcounter will not read the freq
it starts at 000 and ramps up to 999 and then starts over
i hope all of you can help me

steven

Well, that one is easy to fix-- just throw that circuit away. You
don't need three or even two digit precision on the arc frequency. So
a simple analog scale is more than adequate.

Just measure the running frequency and label the freq knob with
approximate frequency settings.

And BTW are you sure this is a good reliable design? The web site says
"preliminary" all over it. You probably don't want to build something
that may be shaky. it's no fun debugging somebody elses design,
especially when debugging can easily result in blown $10 IGBT's, one
after another.
 
K

kidkv

Jan 1, 1970
0
Johnny said:
Does the relay turn on when Q205 is turned on?
Does the output of U201C go fully high, (5V), with the original 4K7 base
resistor, (R226), to Q205 in place? (When you say the Q205 base voltage is
0.71V?
Out of interest, are you making this on a pre-manufactured PCB, or using
other means?
... Johnny

Relays will not turn on when Q205 is turned on. U201C is just under 5V
with the 4.7k resistor. yes they are in place when i got 0.71v
I made the boards with eagle and used a laser printer and used the
toner


the caps are in the one for the power supply and yes i konw one is not
in ther.... but it has power going to it

and it was the best i could find.. and the igbts that i am useing are
packs 200amps

steven
 
J

Johnny Boy

Jan 1, 1970
0
kidkv said:
Relays will not turn on when Q205 is turned on. U201C is just under 5V
with the 4.7k resistor. yes they are in place when i got 0.71v
I made the boards with eagle and used a laser printer and used the
toner

You should consider the possibility of shorts on the board, I guess. (Also,
keep in mind what 'Ancient Hacker' had to say, about the inherent problems
in this circuit. And, as suggested by an earlier poster, a micro-controller
is the right way to go, in my opinion.)
Have you considered that 18V might not be enough to pull in the 24V relays?
In the case of 12V relays, the typical pull-in voltage is about 9V. In the
case of 24V relays, if it's double that and 18V, you're right on the
borderline.
When Q205 is turned off, does it's collector measure about 18V?
And when turned on, what does it measure?
(It seems that your Darlington transistor may be dead, with only 0.7V at the
base, with 5V applied across a 4K7 series resistor) The base voltage sounds
like one forward voltage drop and not two as would be expected.
the caps are in the one for the power supply and yes i konw one is not
in ther.... but it has power going to it

I don't follow this - what do you mean?
 
K

kidkv

Jan 1, 1970
0
Johnny said:
You should consider the possibility of shorts on the board, I guess. (Also,
keep in mind what 'Ancient Hacker' had to say, about the inherent problems
in this circuit. And, as suggested by an earlier poster, a micro-controller
is the right way to go, in my opinion.)
Have you considered that 18V might not be enough to pull in the 24V relays?
In the case of 12V relays, the typical pull-in voltage is about 9V. In the
case of 24V relays, if it's double that and 18V, you're right on the
borderline.
When Q205 is turned off, does it's collector measure about 18V?
And when turned on, what does it measure?
(It seems that your Darlington transistor may be dead, with only 0.7V at the
base, with 5V applied across a 4K7 series resistor) The base voltage sounds
like one forward voltage drop and not two as would be expected.


I don't follow this - what do you mean?
ok with 18v going to the relays i get 8.50v out thats on and off. when
i would take a jumper wire and put it on Collector and Emitter the
darlington would stay on then after some time they would turn off.
i did have a short on the board and got new chip's they got 12v but all
chips are good, and i get an output on the igbts i did put 12amps at
12v in them...

the caps are in the one for the power supply and yes i konw one is not
I don't follow this - what do you mean?

the pdf file that shows the power supply does not show one of the 74
chips for power. and all of the chips have a filter caps.. one thing
i did was i put bigger filter caps in the power supply 3300uf the ones
he used are to small...

steven
 
J

Johnny Boy

Jan 1, 1970
0
ok with 18v going to the relays i get 8.50v out thats on and off. when
i would take a jumper wire and put it on Collector and Emitter the
darlington would stay on then after some time they would turn off.
i did have a short on the board and got new chip's they got 12v but all
chips are good, and i get an output on the igbts i did put 12amps at
12v in them...
<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
 
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