Seconded what a lot of others said -- a) use ohms law to calculate how much current you need to draw based on the resistance b) 9 volt batteries suck. Build one of the hundreds of available power supplies here on ibles.

Consider designing around a bigger battery pack? AA or C or D pack a WAY bigger punch than 9v (technically 6x AAAA), are cheaper (per watt-hour) and easier to find rechargables.

Do you absolutely have to run it on batteries?

Measure the resistance of the length of wire, figure out what voltage you will apply to it, then you know how much current will pull.

thanks, i intend to use this for a fireworks ignitor, so id like it to be portable. it has enough power to make steel wool ignitors work, but they arnt reusable. and did you mean AAA? ive never seen AAAA

because imagine a battery is a pump. a pump that moves electrons (instead of some physical fluid).

The battery size plays a few roles-- generally electrochemical cells put out around 1.5 volts, hence why a 9 volt has 6 AAAA's in there, because volts are a measure of 'pressure' in simple terms, they are good at getting the voltage up when put together. Trouble with them is, they are so compact, there's not a lot of surface area (or volume in this case) for the battery to do its job, so it produces the voltage, but can't spit out enough current. Current is total volume of stuff going from A to B. Total power (watts, generally) is a measure of voltage times amps, so while you have the voltage you need, the smaller batteries can't put out the amperage, and thus can't put out the wattage required to heat the wire.

yeah i have them in a parralel circuit, and the feedwire is much bigger... 16 gauge, however the wires from the control to the detonation area are smaller... this may be half the problem, however when i attatched the nichrome directly to the leads where the detonation wire connect nothing happened. also possibly 6v batteries? like the heavy duty toy car ones?

so if i use a chain of say 6 C batteries with 1 inch of 20 awg nichrome at about 24 gauge. i think that for the sake of portbility im going to possibly put a transformer where the 9vs where and have an external power source that would plug into the control box

. Depends on how much wire you have. . Find out the ohms/ft (or m or whatever unit is convenient) for your wire and multiply by how many feet (or m or whatever) you have. . You know the volts and now you know the resistance - Ohm's Law will tell you the current. Then you can compute your power output (W).

active| newest | oldestb) 9 volt batteries suck. Build one of the hundreds of available power supplies here on ibles.

Do you absolutely have to run it on batteries?

Measure the resistance of the length of wire, figure out what voltage you will apply to it, then you know how much current will pull.

search 'kipkay 9 volt battery hack"

The battery size plays a few roles-- generally electrochemical cells put out around 1.5 volts, hence why a 9 volt has 6 AAAA's in there, because volts are a measure of 'pressure' in simple terms, they are good at getting the voltage up when put together. Trouble with them is, they are so compact, there's not a lot of surface area (or volume in this case) for the battery to do its job, so it produces the voltage, but can't spit out enough current. Current is total volume of stuff going from A to B. Total power (watts, generally) is a measure of voltage times amps, so while you have the voltage you need, the smaller batteries can't put out the amperage, and thus can't put out the wattage required to heat the wire.

. Find out the ohms/ft (or m or whatever unit is convenient) for your wire and multiply by how many feet (or m or whatever) you have.

. You know the volts and now you know the resistance - Ohm's Law will tell you the current. Then you can compute your power output (W).