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Topic: Powering a Heating Element (Read 831 times) previous topic - next topic

TomGeorge

#15
Mar 25, 2019, 02:59 am Last Edit: Mar 25, 2019, 02:59 am by TomGeorge
Hi,
Can you measure voltages A, B and C with respect t gnd, with the Arduino output HIGH and when LOW please?

Thanks.. Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

JCA79B

#16
Mar 25, 2019, 03:01 am Last Edit: Mar 25, 2019, 03:12 am by JCA79B
3.7V across 2 Ohms is 1.85 Amps, what are you powering the heater with? Can it supply 1.85 Amps @ 3.7V?
I'm just wondering if the gate voltage from the ESP is enough to turn the FET full on?
The most intelligent people in the world are the ones who don't think of themselves as the most intelligent person in the world.

lastchancename

That was going to be my question.
Can the battery support the heater?
Forget the ESP for now!
Experienced responders have a nose for laziness, (they were beginners once)... Sure, there are trolls, chest-beaters, and pretenders - but the help you'll get here is about as good as it gets - if you try to help youself!.

Jasonchildress

The battery is a 3.6v Li Ion 400mah pack with protection. here's the datasheet:
https://cdn.sparkfun.com/datasheets/Prototyping/spe-00-502535-400mah-en-1.0ver.pdf

As a test, I have simply plugged the heating element into the battery (on the breadboard) and it has fully powered the heating element:


Now, I'm sure that is not the safest thing to do, but it did work, so because of that I'm assuming "it should" be a sufficient battery.

I have noticed that the more wiring I add to the circuit the lower the voltage becomes (obviously) but I'm suprised by how much. For example, If I took the same direct connection as above and moved the heating element to the other half of the breadboard with jumper cables, the voltage drops from 2.88v to 1.85v.


@TomGeorge, I'll gather those voltage readings for you and get back as soon as I can.

Jasonchildress

hmmm, for some reason my images didn't show up. I've attached them to this post.

Jasonchildress

@TomGeorge, here are the values you requested:

A: ON - 3.56   OFF - 0.0
B: ON - 3.54   OFF - 0.0
C: ON - 2.99   OFF - 0.0

Jasonchildress

I tested this with an 18650 (Samsung INR18650-25R) which according to the datasheet should be more then sufficient. Same results.
http://dalincom.ru/datasheet/SAMSUNG%20INR18650-25R.pdf


TomGeorge

#22
Mar 25, 2019, 05:36 am Last Edit: Mar 25, 2019, 05:38 am by TomGeorge
Hi,
The voltage at A should be the battery voltage ALL the time, ON or OFF.
B should be near 0V when C is at 2.99V, if you are using the correct MOSFET.

Can you post a picture of your project so we can see your component layout?
Can you draw a complete circuit diagram, including the battery connections please?
Draw it with pen/cil and paper and photograph it.
Forget Fritzy.

Thanks.. Tom.. :)  
Everything runs on smoke, let the smoke out, it stops running....

Jasonchildress

I think I probably read my readings incorrectly. I was measuring some of the values from the MOSFET's drain instead of the project's common ground. The following readings are all measured from common ground. These values are probably a bit lower because the battery is starting to drain a bit.

A: ON - 3.18   OFF - 3.18
B: ON - 3.17   OFF - 3.17 (From the drain pin: + on pin, - on common ground)
C: ON - 3.20   OFF - 0.06

I'm confused on how I should measure B. Should I keep the - on the breadboard's common ground and the + on the drain pin? I'm confused because I thought the drain pin should be negative, sourced from ground.

JCA79B

#24
Mar 25, 2019, 06:52 am Last Edit: Mar 25, 2019, 06:58 am by JCA79B
You either don't have the transistor source terminal connected to battery -, or you have blown the transistor. Do you have a spare? The small conductors in a breadboard + iffy connections of too skinny wires cannot handle currents of 1 Amp or more without dropping 1 or more volts.
Do you have some 20 or 22 gauge jumpers with croc clips?
The most intelligent people in the world are the ones who don't think of themselves as the most intelligent person in the world.

Jasonchildress

@JCA79B, I'm using a MOSFET. I switched it out with the same one and I'm still getting the same results.

I do have some 22 AWG wire and I'll try soldering the circuit's wiring instead of using the breadboard to see if that helps.

TomGeorge

I think I probably read my readings incorrectly. I was measuring some of the values from the MOSFET's drain instead of the project's common ground. The following readings are all measured from common ground. These values are probably a bit lower because the battery is starting to drain a bit.

A: ON - 3.18   OFF - 3.18
B: ON - 3.17   OFF - 3.17 (From the drain pin: + on pin, - on common ground)
C: ON - 3.20   OFF - 0.06

I'm confused on how I should measure B. Should I keep the - on the breadboard's common ground and the + on the drain pin? I'm confused because I thought the drain pin should be negative, sourced from ground.
To measure B, put positive probe on B and negtative probe on common gnd.
Then turn ON and OFF.
Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

JCA79B

OK, but leave your WeMos disconnected for the time being until you get the MOSFET, heater and battery working right.
Connect one heater lead to batt +, the other heater lead to MOSFET Drain (center pin),MOSFET Source (right pin) to batt -, connect a 10k resistor between MOSFET Gate (left pin) and batt -, momentarily connect a wire from Gate to batt + to test.
The most intelligent people in the world are the ones who don't think of themselves as the most intelligent person in the world.

Jasonchildress

#28
Mar 25, 2019, 07:47 am Last Edit: Mar 25, 2019, 07:50 am by Jasonchildress
@TomGeorge: OK, that's what I did, and those are the results I got. Maybe I just don't have the correct MOSEFT.

Because the many MOSET values confuse the heck out of me, what do you guys think is the best one for the job? I'm open to SMD suggestions also as eventually I'd like to shrink this project down after I get past this initial prototype phase.

@JCA79B: I started to solder this up, but ran into some issues with the solder adhering to the heating element's body (-). I've been going at this all day today so I need to sleep ATM. I'll pick this up again tomorrow after work.

Thanks everybody for the support tonight.

TomGeorge

Hi,
How about a picture of your project so we can see your component layout?

When you did what @JCA79B suggested in post #27, what happened when you connected a wire from gate to battery positive?

Thanks.. Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

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