3.7v heating coil with Microcontroller

Thread Starter

twin86

Joined Oct 24, 2017
7
I'm try to developed a electronic lighter with a micro controller inside to control every time that i turn on one cigarette.
All circuit is done and works fine in terms of microcontroller firmware. The problem is when I every time try to turn on the Heating coil, the micro controller goes down and make reset. The problem is that the heating coil need a lot of current and make shurt circuit to the battery.
How can I resolve this problem?
Below you can see part of circuit.
 

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philba

Joined Aug 17, 2017
960
Microcontrollers don't like the supply voltage pulled down which is what's happening with a heavy current draw. Use a capacitor to smooth the power to the micro and a schottky diode to prevent the load from "stealing" power from the cap. You will need to determine the cap size experimentally and it may be significantly larger than you want depending on how long/much the load pulls the +V rail down. The schottky diode has a smallish voltage drop (0.2 to 0.4V or so) which will lower your micro's supply by that so you may need to deal with that. Don't use a silicon diode which has about double the drop.
diode protec PS.png
 

Thread Starter

twin86

Joined Oct 24, 2017
7
Hello Max,

Thanks for the replay but i'm using a LiPo battery : HCC1040, 3.7v 240mah 15C-rate diameter*height 10*40mm) and not resolved the issue.

Best regards
 

Dodgydave

Joined Jun 22, 2012
10,093
Hello Max,

Thanks for the replay but i'm using a LiPo battery : HCC1040, 3.7v 240mah 15C-rate diameter*height 10*40mm) and not resolved the issue.

Best regards
There's your problem, the battery can't supply enough current, you need 2.7amps at least for the ignition coil...
 

Thread Starter

twin86

Joined Oct 24, 2017
7
Thanks Philba.

Basically you suggest using a cap and a diode to protect the micro. But I have other components that also go down like BLE modulo, EEprom and regulator. Do you think that I can put the cap and the diode connect to the regulator output, and with this away a can protect all the VCC line of the drop voltage?

Best Regards

Why do you need a micro + FET just to switch on a heater? Wouldn't s simple push-button do the job?
Hello Alec_t

I used a micro to be able communicate via BLE with a smart phone app.

Thanks in advance.

There's your problem, the battery can't supply enough current, you need 2.7amps at least for the ignition coil...
Hello,

Maybe a Super capacitor in parallel with the battery can help?

Thanks in advance
 
Last edited by a moderator:

philba

Joined Aug 17, 2017
960
Thanks Philba.

Basically you suggest using a cap and a diode to protect the micro. But I have other components that also go down like BLE modulo, EEprom and regulator. Do you think that I can put the cap and the diode connect to the regulator output, and with this away a can protect all the VCC line of the drop voltage?

Best Regards
Sure, put all the stuff that needs protection behind the "firewall". You might well wind up with a super cap but remember that it might have a pretty ferocious charging rate.
 

BR-549

Joined Sep 22, 2013
4,938
I like most others believe the processor is losing voltage upon coil enerization. You should verify this first. Have you got a meter that can capture max and min? How about a scope...got one?
 

Thread Starter

twin86

Joined Oct 24, 2017
7
I like most others believe the processor is losing voltage upon coil enerization. You should verify this first. Have you got a meter that can capture max and min? How about a scope...got one?
Hello,

I can confirm, Every time that I energize the coil the voltage drop down to 2.2v. I measure and check. And yes I got one scop.

Thanks in advance.
 

Reloadron

Joined Jan 15, 2015
6,225
You have a 1.4 ohm heating element and a 1.5 amp current draw. You reflect a 3.7 volt 240 mAH battery. How long for your heating element to glow? I simply do not see your battery being able to handle the load, even for a short period of time. I see where you just posted the voltage drops to 2.2 volts. What is the heating element actually rated at, voltage and current? Less a bigger power source I do not see this as working. I also agree all you need is a push button, heater element and a supply capable of driving the element.

Ron
 

BR-549

Joined Sep 22, 2013
4,938
Have you looked at the firmware......and see if gate signal is modulated? Or just scope coil as you flick your bic.
Is the coil voltage steady or pulsed?
 

BR-549

Joined Sep 22, 2013
4,938
If this is a proven design.......I'm going to guess a needed duty cycle adjustment. This firmware you acquired.....was it for this circuit components?.......or are you experimenting?
 

Thread Starter

twin86

Joined Oct 24, 2017
7
You have a 1.4 ohm heating element and a 1.5 amp current draw. You reflect a 3.7 volt 240 mAH battery. How long for your heating element to glow? I simply do not see your battery being able to handle the load, even for a short period of time. I see where you just posted the voltage drops to 2.2 volts. What is the heating element actually rated at, voltage and current? Less a bigger power source I do not see this as working. I also agree all you need is a push button, heater element and a supply capable of driving the element.

Ron
Hello Ron,
I just need active the heating coil during 5s. I controlled the time via micro-controller. The heating coil was rated for 3.7v and 2A max. I don't need 2A to turn on one cigarette. 1.5A it is enough. I need a micro controller to register the hour and date with a internal RTC. Basically I wanted make e electronic lighter as this with more intelligent.


Thanks in advance.
 

Reloadron

Joined Jan 15, 2015
6,225
Then I would try it just direct from the battery using a switch or push button. I understand your use of the micro but since the voltage drops so much question the ability of the battery.

Ron
 
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