help with shorting probem on my curcuit

This circuit does not work because of a problem with power shorting to ground at the motor. I think that is the only problem. The servo provides a 4.5v power source and the polarity can switch allowing the original 4.5v servo motor to run forward and reverse. I am making this to run a motor on 12v and the servo on 4.5v. R1 keeps the transistor saturated and the R2 is in there because I read it would help the transistor turn off completely. I made this circuit work (the right voltages went to the right places) in one direction but now it is more complex, I think I’m having a shorting problems. Can anyone help?

Topic by kendallickes   |  last reply


Disposable camera hack? Answered

Hi, im building a capacitor bank for my coilgun, and I have 17 disposable camera capacitors in them. (wired in parallel (or whatever one means + is atached to +, and - is atached to -)) But for some reason wenever I start chrging it, after a little wile, it makes a huge spark across one of the capacitors. That probobly means its arcing right? but its only 300 volts (there wired in parelell so only the amperage goes up, not the volts). I then tryed to charge the caps to a point before they arced, wich took about 1 min (the battery is full) and my ammo only shot 3 inches! 17 capacitors, charging for 1 min, and it slid across the floor 3 inches! I have no idea what im doing wrong. Im using wire from a microwave motor (wich is realy small) for the coil, and its 5 layers thick, wrapped around a hollowed out pen. So, to sum it all up, here are the main problems: 1) the caps arc when charging 2) the ammo only goes 3 @#%!ing INCHES!!!!!! arg! Ps, i heard someware, that if you have enought amps, it will arc even with lower voltages. Maby thats whats happening? PLEASE HELP!!!!!! :(

Question by Stuffses   |  last reply


Disposable Camera Hack?

Hi, im building a capacitor bank for my coilgun, and I have 17 disposable camera capacitors in them. (wired in parallel (or whatever one means + is atached to +, and - is atached to -)) But for some reason wenever I start chrging it, after a little wile, it makes a huge spark across one  of the capacitors. That probobly means its arcing right? but its only 300 volts (there wired in parelell so only the amperage goes up, not the volts).  I then tryed to charge the caps to a point before they arced, wich took about 1 min (the battery is full) and my ammo only shot 3 inches! 17 capacitors, charging for 1 min, and it slid across the floor 3 inches! I have no idea what im doing wrong. Im using wire from a microwave motor  (wich is realy small) for the coil, and its 5 layers thick, wrapped around a hollowed out pen. So, to sum it all up, here are the main problems: 1) the caps arc when charging 2) the ammo only goes 3 @#%!ing INCHES!!!!!! arg! Ps, i heard someware, that if you have enought amps, it will arc even with lower voltages. Maby thats whats happening?

Topic by Stuffses   |  last reply


Calculate Resistor for Heating Wire

Hi there, My Goal is to use a piece of heating wire from an old hair dryer  (1.6 Ohms resistance for the length i want to use.) and heat it red-orange using my old USB power bank. 5V output from an 3.8V lithium ion battery i dont want to mess with the circuitry inside. Problem: The USB Power Bank has short curcuit prevention built in, so when i connect the heating wire the power bank stops supplying electricity. I found a 7.5 ohms resistor and connected it aswell, the wire became a little warm, the resistor incredibly hot but most importantly the power bank continued to supply power - success. I would like to know what resistor i should use to get the wire red-orange hot but at the same time keep the power bank safe and not overwhelm it - i think that would mean not drawing too much current? I also cant check how much current is flowing because my multimeter is too cheap and only goes up to 200ma, which the power bank exceeds. So how would i go about this? What resistor should i use for what wattage should it be rated. And since im a total newb id like to hear your train of thought as to why and how. Thank you so much.

Topic by emiliori   |  last reply