I'm trying to burn a 1ohm resistor. I did it once before from a Nano that feeds a fqp30n06 mosfet that uses a 9v battery thru the resistor. I activated the gate from a pin on the nano (via code) and the current fed thru the resistor and burnt it.

I'm trying to repeat the task but the resistor won't burn, it won't even get hot. The gate is activated via code still, I can read the 9.34v across the header pins where the 1 ohm resistor normally sits, so I know the code and wiring is fine.

What else could be wrong?

 

Why are you trying to burn a resistor? The object is NOT to burn parts. Why would you want to risk frying your nano?

 

Hello,

Show us the schematic of your set-up.
What is the power rating of the resistor?



Bertus

 

Why are you trying to burn a resistor?

Firewood scarce, perhaps?

 

1/4W resistor
The resistor is wired across the diode, on the female header pins.

 

Firewood scarce, perhaps?

I used to think there were no stupid questions. You proved me wrong because I guess I asked one when the answer was so obvious.

 

1/4W resistor
The resistor is wired across the diode, on the female header pins.

View attachment 166874

This is a schematic. See how much easier that is to follow other than trying to trace out the wires in a drawing? Why are you trying to burn up a resistor?

 

Hello,

I assume the resistor is accross the diode in the drawing.
The problem lies likely in the mosfet.
Looking at the datasheet the VGS(th) is between 2 and 4 Volts.
It could well be that the mosfet is not turned on.

Bertus

 

Hello,

I assume the resistor is accross the diode in the drawing.
The problem lies likely in the mosfet.
Looking at the datasheet the VGS(th) is between 2 and 4 Volts.
It could well be that the mosfet is not turned on.

Bertus

I don't think we should be encouraging the TS to engage in poor practices. I see no practical purpose to burn a resistor.

 

Hello,

I assume the resistor is accross the diode in the drawing.
The problem lies likely in the mosfet.
Looking at the datasheet the VGS(th) is between 2 and 4 Volts.
It could well be that the mosfet is not turned on.

Bertus

It is ON because when I replace a resistor with leads to a mmeter I get all 9.34V across the headers where the R goes.

 

It is ON because when I replace a resistor with leads to a mmeter I get all 9.34V across the headers where the R goes.

What voltage do you get with the resistor still connected?

 

Hello,

A voltmeter has a very high input impedance (most DMM's have an input impedance of 10 to 20 MegaOhms in the voltage range).
The mosfet will likely conduct a very low current.
Place a resistor of 1K accross the meter and measure the voltage again.

Bertus

 

What else could be wrong?

Are you sure it's a one ohm resistor in your second attempt?
SG

 

Hello,



Using the formula R=Voltage * Voltage / Power, any 1/4 Watt resistor smaller than 330 Ohms would burn.
The lower the value, the faster it will burn.

An other problem could be the battery power.
9 Volts accross a 1 Ohm resistor would result in a current of 9 Amperes.
A PP3 battery will never deliver that amount of power.

Bertus

 

Logic level mosfets will have it's Rds(on) resistance specified for 4 to 5 volts Vgs. The datasheet for your mosfet specifies it at Vgs=10v, so it's NOT a logic level mosfet. A 9v battery isn't going to be very happy with a 1 ohm resistor across. Check the battery voltage with the 1 ohm resistor across. And in fact, connect the resistor directly to the battery for that test, to see if it burns. Do not burn your fingers.
Why would you like to burn the resistor in such an elaborate manner, anyways?

 

I don't think we should be encouraging the TS to engage in poor practices. I see no practical purpose to burn a resistor.

The purpose is clear: It is to ignite the trigger fuse for an explosive device. They work very well in that application, being just slow enough to not detonate in response to noise spikes. The makers of IEDs are becoming more clever every day. And now there is some way for the arduino board to detect a passing truck while ignoring passenger cars.

 

I can read the 9.34v across the header pins where the 1 ohm resistor normally sits, so I know the code and wiring is fine.

So, measure across the resistor which is likely open.

The purpose is clear: It is to ignite the trigger fuse for an explosive device. They work very well in that application, being just slow enough to not detonate in response to noise spikes. The makers of IEDs are becoming more clever every day. And now there is some way for the arduino board to detect a passing truck while ignoring passenger cars.

Been there and done that using a 1 Ohm resistor as an igniter for black powder charges.

Anyway,you are sure your resistor isn't open? I have seen simple 1 Ohm resistors read infinity. Especially low wattage ones like 1/4 or 1/8 watt.

Ron

 

I measured as follows:

1. Replacing resistor leads with multimeter leads....9.34v

2. Measuring across both 1 ohm and 1k ohm, about 0.01V and 0v respectively. Although I doubt my meter goes that low.

And it's for igniting a rocket remotely based on a program as a science project that I've been working on since last year. I even posted about it last year. It's one of those estes rockets. We don't mess around with ieds in my little third world country, we leave that to sophisticated first world countries.

Thanks Bertus and Reloadron and Albert

 

So it sounds like the MOSFET isn't getting enough gate voltage to turn fully on. You need a logic level MOSFET to ensure that the Arduino can turn it on.

 

A 1.0 Ohm resistor should work. The Estes Igniter #302301 is about a 0.8 Ohm resistance and they normally fire these things with a 12 Volt lead acid battery.

I have used the MOSFET you are using with an Arduino and driving about a 0.5 Amp load, maybe only 400 mA as it was a RGB LED string but it worked fine using 5 Volts from an Arduino with a 10K gate resistor to ground. Pretty much as you drew it. This is also a good read from Estes if you haven't read it. Anyway while a 9 volt battery is not the best choice it should work as it did before for you. Something is not allowing enough current. You could try a fresh battery?

Ron