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Yes, it simply turns on when the voltage at pin 2 is higher than pin 3... whatever is present. A voltage divider is suggested to draw minimal current from the cap, though. Just make the resistors very high values.
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nice looking setup manI was also thinking about doing one with the caps on the outside for easy switching and it kind of gives it a retro look like an old tube setup, all you need now is an analog voltage display. what where those connectors you used called?
They are deans connectors....they are a typical rc connector
It might be advisable to put a small value cap on pin 2 to ground - I'm not sure if the spark that is produced in welding will do any damage to the op-amp input from possible spikes. A .01µF or .001µF cap would probably do. Or just wing it and see what happens. That's what I would do!
I got a couple of each but the 339 14pin seems like overkill, but I figure it might come in handy for something
I'm pretty sure I enjoy building and learning this stuff more than anything.
Woot woot....dsy5 it works!
I had to switch 2 & 3 to get voltage when the cap was charged....and I didn't put in the voltage divider yet so it does draw down the cap pretty fast....but conceptually it works.
I changed out the on off switch to a dual pole and put in a resistor to drain the cap when switched off.
I also added a dual pole momentary button to change the display meter to see the cap voltage when pushed.
I still need to figure out how/where to get to the voltage adjustment, add the voltage divider, and clean up the wiring.
The red led is not nearly as bright as it seems in the pic.
I had to switch 2 & 3 to get voltage when the cap was charged....and I didn't put in the voltage divider yet so it does draw down the cap pretty fast....but conceptually it works.
I changed out the on off switch to a dual pole and put in a resistor to drain the cap when switched off.
I also added a dual pole momentary button to change the display meter to see the cap voltage when pushed.
I still need to figure out how/where to get to the voltage adjustment, add the voltage divider, and clean up the wiring.
The red led is not nearly as bright as it seems in the pic.
Very nice! It's been awhile since working with comparators, so sorry for the reversed inputs
. I had the same idea for draining the cap with the DPDT switch. Not sure you need to read both the supply and the cap with the MM LED since the cap will always charge to the supply voltage after 5 time constants - pretty fast without a large limiting resistor. And besides, once you get the comparator set up properly, the charge LED will tell you!Just a thought, but if a transistor was fed by the output of the comparator, when the cap attained the proper voltage, the transistor would conduct. If the output of the cap was tied to the transistor collector and the positive weld lead connected to the emitter, it would supply the charge to the wires. In that way, the wires could be touching and with a push of the button they would weld themselves!
The welding action, although, could be dependant on the spark generated when the wires are touched together; so this may not work as expected. I guess an experiment is necessary!
The welding action, although, could be dependant on the spark generated when the wires are touched together; so this may not work as expected. I guess an experiment is necessary!
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I simulated the transistor action by having the NR-R wires touching and then plugging the positive weld lead into the original camera board unit - the wires welded! I need to build up the op-amp comparator and add a transistor. I also need to make up the LM2577 unit. It's off to the junk box to see if I have any of the components necessary on-hand, or if I need to make a road trip.
dsy5
I agree on the display switch. I shouldn't have mounted in the box, I just wasn't sure I would get the op-amp working.
The transistor thing sounds interesting, can't wait to hear if it works. I wish I hadn't fried my other LM so I could have one setup on bread board.
I agree on the display switch. I shouldn't have mounted in the box, I just wasn't sure I would get the op-amp working.
The transistor thing sounds interesting, can't wait to hear if it works. I wish I hadn't fried my other LM so I could have one setup on bread board.
Damn, since there is no load for the transistor other than essentially a short, the voltage will always be present at the emitter. Therefore, either the cap won't charge or will spark without being triggered. Maybe an inductor as a load will do the trick - and I don't believe I have any lying around. Maybe a relay as the load...
dsy5.....when I try to add the voltage dividers it's no bueno.....I have tried my 2&3 voltages down around 1-3v
The one thing about your schematic that I'm not familiar with is the loop back arrow at the bottom left for the cap voltage resistor to ground.
That is a potentiometer - wired as as rheostat. The pot should actually be in the LM2577 leg; I'll have to repost it (I'll change the inputs,too).
Resistor values should all be around 100kΩ (except for the one near the LED; about3.9kΩ). When you vary the pot the reference voltage will drop and the cap will be slightly higher in voltage than the LM2577 reference voltage.
I have taken a simple approach to this...
I have a fuji circuit, to which I've soldered the charge button shut. I have removed the resistor between charge LED and ground.
I have taken 4 caps from other cameras, and paired them parallel.
I have the following circuit on the positive lead of caps, and grounded it to the battery.
I am not an electrical designer, just a hobbyist, but this works for me. I have used multiple senders, as the can be shorted with a dip switch, to get lower voltages, if desired.
The circuit when powered by a aa battery, charges the caps to about 65 volts, causing the led to glow. At that time welding is possible. The circuit cycles, discharges in about 70 seconds. If you miss the highest LED glow, wait for the next one.
Simple, cheap, it works for me!
I have a fuji circuit, to which I've soldered the charge button shut. I have removed the resistor between charge LED and ground.
I have taken 4 caps from other cameras, and paired them parallel.
I have the following circuit on the positive lead of caps, and grounded it to the battery.
I am not an electrical designer, just a hobbyist, but this works for me. I have used multiple senders, as the can be shorted with a dip switch, to get lower voltages, if desired.
The circuit when powered by a aa battery, charges the caps to about 65 volts, causing the led to glow. At that time welding is possible. The circuit cycles, discharges in about 70 seconds. If you miss the highest LED glow, wait for the next one.
Simple, cheap, it works for me!
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ok I will give that a try
below is the simple way I have the 741 hooked up and it works (kinda as described earlier)...hooking up the 339 the same way doesn't work at all. A weird thing about the 741 is that when no voltage is coming from the cap I get 12v from somewhere.
would the 339 be hooked up the same as your latest schematic?
No, LM339 is a comparitor and the inputs are swapped. (That's why my first schematic was wrong - I was wiring as I would a LM339
) A diode would probably solve the 12V problem - I take it you mean 12V on the cap.
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