need help with capacitance and slow discharge!

i need to make a slow dishcharge capacitor bank capable of discharging 12 volts at about half an amp over about 5 seconds. What sort of capacitor and resistors should i use? It will be powering a short length of nichrome.  thanks :)

Without clever electronics, the capacitor will discharge exponentially, the voltage will decay from a maximum value, and current will follow it.

If you equate the ENERGY dissipated to energy stored in the cap, then IVt = 12 x 0.5 x 5 = 30 Joules....

For the capactitor E=CV^2/2 so 30 x 2/12^2 = 0.4 Farad.

If you aren't careful, the initial discharge will blow your wire.

kretzlord (author)  steveastrouk6 years ago
thank you both :)
seandogue6 years ago
With the requires you specify, you'd be better off using SLA batteries or something similar rather than wasting time trying to do it with capacitors.