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Registered Member #1854
Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88
i know putted most bugs out of the scheme but i notice something when my caps are charged.
my supply current increases slowly, that is a problem because if i later use a battery in my portable coilgun, when the capacitors are charged they gonna suck the battery dry. so can't something be done so that when my caps are charged the current fall's to zero so the battery is spared ?
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
This is usually done. On the output, a comparator is placed. When the comparator triggers, the output goes high. This output connects to the reset pin (pin 4 on the 555) wich turns it off. This has the added benifit that it will ocasionally turn on, to keep the capacitor charged. Check out anothercoilgunsite.com for a schematic.
Also, what battery are you using? Its a good idea to use lithium ion, due to there power/size.
Registered Member #1854
Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88
im now using just a power supply my schematic is still in its testing fase, a friend of me has a motorcycle battery its not to large and we are planning to use it.
i use a comparator LM311N, and when my capacitors are charged the LED lights up, but the current still increases instead of decreasing.
Registered Member #1854
Joined: Wed Dec 10 2008, 06:09PM
Location: West-Flanders Belgium
Posts: 88
yeah those analog meters do look good on a cap bank, but the whole coilgun setup must be portable, and we've made a small control panel that will fit on the back of the gun and there are drilled holes in there (2 for leds) : one for the on/off indication and one who indicates if the cap bank is charged.
i have thought of getting a LED in series with a large resistor over the cap bank and when the voltage is 400 the LED will light up at its maximum, but that is something i would do if nothing else works. because i don't want to have wires to the control panel that carry 400V
so aren't there any other ways to have an indication led that won't pull up the voltage at pin 4?
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
You could probably connect an LED to the output of the LM311 as depicted in the schematic, and then use a small signal NPN transistor to relay the same signal from the LM311 to the 555 timer.
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