Hot wire cutter wall wart not working

MrClean

Well-known member
Did you measure the resistance of your wire? .3 amps at 12 volts would put your wire at 40 ohms of resistance. If you increase the resistance you will decrease the current. Your walwart is good for 12 volts at 2 amps which would be 6 ohms of resistance minimum. Anything less will be more amps then your walwart is capable of. Like short circuiting. It usually takes a bit of that to burn them out though. Meter the output with no load and see if it's putting out 12 volts. If it isn't, it's cooked. Also meter your wife, perhaps it is higher resistance then needed.
 

agupt108

Member
Did you measure the resistance of your wire? .3 amps at 12 volts would put your wire at 40 ohms of resistance. If you increase the resistance you will decrease the current. Your walwart is good for 12 volts at 2 amps which would be 6 ohms of resistance minimum. Anything less will be more amps then your walwart is capable of. Like short circuiting. It usually takes a bit of that to burn them out though. Meter the output with no load and see if it's putting out 12 volts. If it isn't, it's cooked. Also meter your wife, perhaps it is higher resistance then needed.
It ouputs 12.24 v without any load, just the circuit itself.
 

agupt108

Member
So if that is the case, any ideas as to why the wire does not heat? Maybe from (
) 4:53...I have actually almost the same power supply.
 
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MrClean

Well-known member
I'm assuming it's a multi-meter? Can you measure the resistance of the wire on your cutting bow, from clip to clip NOT with the power supply hooked on just from where you clip your power cables to.
Also, be aware most Multimeters have two amperage measurement inputs that are seperate from your Voltage, Ohm, diode test hookup. These are all marked in Red usually with the one common being a black socket for your black cable. Low amperage (300 ma in my Fluke) goes through one socket any other current up to 10 Amps goes through the other. When you put the meter in either amperage reading it disconnects the Volt Ohm diode test port and reads from the other two ports. If you don't change your lead it should read nothing. Change to the High amp port first to make sure you are not trying to measure anything over the low ports capability. Put over 300ma in my low port and you'll smoke a fuse. Go over 10 in the High port and you'll smoke a different fuse. Important to read the meters instructions. We need to measure your load so we know what the amperage should be. If it acts like an old lightbulb the resistance will go up a bit when hot but base load should tells us how much your dealing with.
 

agupt108

Member
I'm assuming it's a multi-meter? Can you measure the resistance of the wire on your cutting bow, from clip to clip NOT with the power supply hooked on just from where you clip your power cables to.
Also, be aware most Multimeters have two amperage measurement inputs that are seperate from your Voltage, Ohm, diode test hookup. These are all marked in Red usually with the one common being a black socket for your black cable. Low amperage (300 ma in my Fluke) goes through one socket any other current up to 10 Amps goes through the other. When you put the meter in either amperage reading it disconnects the Volt Ohm diode test port and reads from the other two ports. If you don't change your lead it should read nothing. Change to the High amp port first to make sure you are not trying to measure anything over the low ports capability. Put over 300ma in my low port and you'll smoke a fuse. Go over 10 in the High port and you'll smoke a different fuse. Important to read the meters instructions. We need to measure your load so we know what the amperage should be. If it acts like an old lightbulb the resistance will go up a bit when hot but base load should tells us how much your dealing with.
The multimeter reads 2.6 ohms for about a foot of guitar e string from clip to clip
 

MrClean

Well-known member
that would be close to 5 amps, you'll either burn out your supply or it will crowbar and stop putting out over 2 amps. For maximum rated output you need 6 ohms in your circuit. IF you're showing 12 volts under no load and 0 hooked up, I'd say it's shutting down with the load. Try getting a higher load and hooking that up and see if you maintain the 12 volts or if ANY load now drops the output voltage to zero. Ohms law is pretty basic. Current = Voltage over Resistance. OR Resistance equals Voltage over current. Gives you things to test. It's also possible I guess for this power supply to put out just the 24 watts (watts-Voltage times current 12 volts x 2 amps 24 watts.) If the power supply is putting out 24 watts at a maximum of 12 volts or 2 amps we can expect your voltage displayed at that power level to be 7.9Volts. But it may just shut down sensing a short or overcurrent.