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Hey guys, I'm new here and I want to make a 9 V lighter/igniter.

I used a short nichrome wire from our broken oven toaster, locked it in with two short bolts and hooked it up to a doorbell switch since its hard to find a proper small switch where Im from. I used a 9 V battery to power it. When i turned it on it did feel warm but the nichrome wire didn't turn red hot.

Is there anything wrong that I'm doing? Should I turn the nichrome wire? I was hoping to used a straight nichrome wire instead of using loops. Am I using the wrong kind of wire? I'm using 0.30mm^2X2C speaker wire. Should I up the power by using two 9 V batteries?

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    \$\begingroup\$ This is so "Heath Robinson" - why not add two more nuts and secure the feed cables to prevent a mishap? \$\endgroup\$ – Solar Mike Oct 29 '17 at 9:27
  • \$\begingroup\$ I did add two more nuts but still didnt work \$\endgroup\$ – Lancelot Dela Torre Jr. Oct 30 '17 at 10:47
  • \$\begingroup\$ did you read, and act on, the two answers you have been given? \$\endgroup\$ – Solar Mike Oct 30 '17 at 10:48
  • \$\begingroup\$ Yup. Even changed the toaster nichrome wire with a hair dryer's since my uncle had some to spare. Used a small length of it. Still nothing but its hotter than it was last night. \$\endgroup\$ – Lancelot Dela Torre Jr. Oct 30 '17 at 12:33
  • \$\begingroup\$ Work on not only length but diameter... \$\endgroup\$ – Solar Mike Oct 30 '17 at 12:35
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'A 9v battery' is probably woefully under-powered to drive the wire you have, assuming you mean the usual PP3 size.

Toaster wire will usually require a current in the low amps ballpark to glow red. A PP3 battery is good for low tens of mA continuously, low hundreds of mA if short-circuited, and is quite inadequate.

If you want to try two PP3 batteries, then putting them in parallel to increase the available current would give you a slightly less bad solution, but still be unlikely to make the wire glow. Once you're up to several dozen parallel PP3s, you might hope for success. However, a more appropriate battery type or power supply would be better.

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  • \$\begingroup\$ Hey thanks for the answer. I did chabge the nichrome wire to a haidryer's and its hotter than before but still not glowing red. Should I change the switch? \$\endgroup\$ – Lancelot Dela Torre Jr. Oct 30 '17 at 12:54
  • \$\begingroup\$ you may well damage a doorbell switch connecting it to a load like this, but it's unlikely the switch itself is the problem. The problem is your source of power is too weedy. \$\endgroup\$ – Neil_UK Oct 30 '17 at 13:11
  • \$\begingroup\$ No worries. I showed it to my uncle and he made me try it out without the switch and it worked 😀 thank you! Now Im gonna try and find a better switch or just make my own. \$\endgroup\$ – Lancelot Dela Torre Jr. Oct 31 '17 at 14:01
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You can calculate the required volts per centimeter of wire as follows:

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. Possible element connection patterns in your toaster. You need to measure the total length of wire on one circuit from L to N.

  • Measure the total length of nichrome wire in one circuit of your toaster. (All the elements may be in series or there may be two or four in parallel across the mains.)
  • Read the mains voltage from your toaster.
  • Calculate the volts/cm by dividing volts by cm.

e.g If we have a 230 V toaster and find that the element length is 60 cm then the volts/cm = 230/60 = 4 V/cm (approximately).

Now if you have a decent 9 V battery you could power 9/4 = 2.25 cm of wire and get the same glow as your toaster.

What about current?

We can work out the current of the toaster by reading it from the toaster nameplate. Divide that by the number of circuits to get the current per wire. e.g., The toaster is rated at 5 A but our examination showed that there were two parallel circuits so they must take 2.5 A each. Then you can compare this value with your battery specification to see if it's powerful enough.

If the toaster nameplate doesn't give the current (amps) rating but gives power (watts) then calcuate the current rating from \$ I = \frac {P}{V} \$ where I is current in amps, P is power in watts and V is voltage in volts.

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  • \$\begingroup\$ Thank you for the answer! I did take into account length of the nichrome wire and also changed it to a hairdryer's nichrome wire. Wprked like a charm after I took off the switch and tested it 😀 \$\endgroup\$ – Lancelot Dela Torre Jr. Oct 31 '17 at 14:03

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