Help! Having problem with Mosfet/Charger

[fasteddie600]

Aaargh, so close to finishing the electronics for another mod. Doing a final fit before I paint the box, and having a couple of issues.

I am building into a Hammond enclosure and fancied having a go at a Mosfet build as not tried one before.

I am building a 2x18650 mod using this Mosfet-http://www.modmaker.co.uk/Mod-Making-Supplies/components/n-channel-mosfet-80A-55V

I have followed the wiring diagram below and everything fires up, only problem is when i put the USB charger into it's slot it fires. I have figured out this is because the charger itself is now creating an negative connection back to the atty through the case, if I pull it out it stops firing. Also noticed the atty is slow to fire using the Mosfet circuit and much more fierce when firing due to charger being in?

If anyone has any suggestions how to get round the charger issue, I would like to keep the cut out as is if pos for the usb as it sits in lovely and snug. Also anyone know why its not firing full force with the resistor specs as per the diagram?

Any help much appreciated.

 

[fasteddie600]

Forgot to add, not that I think it makes any difference, I am have added a Voltage Display. This is connected from slide sw out to bat -ve, I wanted it on whenever the box was turned on.

 

[RicModMaker]

Aaargh, so close to finishing the electronics for another mod. Doing a final fit before I paint the box, and having a couple of issues.

I am building into a Hammond enclosure and fancied having a go at a Mosfet build as not tried one before.

I am building a 2x18650 mod using this Mosfet-http://www.modmaker.co.uk/Mod-Making-Supplies/components/n-channel-mosfet-80A-55V

I have followed the wiring diagram below and everything fires up, only problem is when i put the USB charger into it's slot it fires. I have figured out this is because the charger itself is now creating an negative connection back to the atty through the case, if I pull it out it stops firing. Also noticed the atty is slow to fire using the Mosfet circuit and much more fierce when firing due to charger being in?

If anyone has any suggestions how to get round the charger issue, I would like to keep the cut out as is if pos for the usb as it sits in lovely and snug. Also anyone know why its not firing full force with the resistor specs as per the diagram?

Any help much appreciated.

That shouldn't happen. Have you tried a continuity test using a multimeter? Maybe something is shorting out on the case? Might be time to bust out the insulation tape

 

[fasteddie600]

The problem is the box being metal, it never ocurred to me that the USB would create an negative loop through the charger- specifically the usb socket surround.

I am now making a small acrylic insert to insulate the socket area, everything else is working fine without insulation but I will be insulating and gluing parts into place to be sure.



I have been testing with the meter whilst the electronics are out, and I am still getting a slow ramp up on voltage. Starts off when fired around 2 volts then gets over 3 after 4-5seconds. Is that normal?

I dont think my wiring is too small I have used 2.5mm cable for main conductors and 1.5mm for the other bits. I have tested all the switches and they appear to be working ok.

 

[RicModMaker]

The problem is the box being metal, it never ocurred to me that the USB would create an negative loop through the charger- specifically the usb socket surround.

I am now making a small acrylic insert to insulate the socket area, everything else is working fine without insulation but I will be insulating and gluing parts into place to be sure.



I have been testing with the meter whilst the electronics are out, and I am still getting a slow ramp up on voltage. Starts off when fired around 2 volts then gets over 3 after 4-5seconds. Is that normal?

I dont think my wiring is too small I have used 2.5mm cable for main conductors and 1.5mm for the other bits. I have tested all the switches and they appear to be working ok.

Glad you sussed that one. That's exactly what I did when I built my first mosfet build.
Not sure about ramp up, that's above my experience. Where's sparkyjuice?

 

[sparkyjuice]

Are you measuring voltage with a load on fasteddie600 ?


Sent from (who cares) using Planet of the Vapes

 

[fasteddie600]

Glad you sussed that one. That's exactly what I did when I built my first mosfet build.
Not sure about ramp up, that's above my experience. Where's @sparkyjuice?

Yep the usb issue all sorted now, TY.

Still getting slow fire issue, I have tested the board and couldn't find a problem. I have made a new board tonight with new mosfet, resistors, tactile switch, and led. Still the same issue, very slow to fire up? Any ideas what I might be doing wrong?
I haven't replaced the voltage display as I only have one, and also I haven't replaced the main switch or charger, but i cannot detect any issue there.
It does eventually get going, volt display is saying 4v with about .1v drop when firing. Do I need a very low resistance atty to get this firing better tried 0.9ohm on there and it's not much better?
I am getting 4.05V at G, 0V at S, and around 2V on D pins when firing and 2-3v on 510 which slowly ramps up. Maybe someone out there knows what that may indicate?

 

[fasteddie600]

Are you measuring voltage with a load on @fasteddie600 ?


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Hi sparky,

Yes I am measuring with a 2.0ohm atty attached, the voltage across the 510 starts off as low as 1.5 and slowly makes it up to around 3.2 after 10-15seconds. Battery voltage remains around 4v.
I tried with a 1ohm load and that didn't make a real difference.

Without load I am getting 4v at 510.

 

[sparkyjuice]

Try a stupid low ohm load and see what happens say 0.3 ohm


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[fasteddie600]

Try a stupid low ohm load and see what happens say 0.3 ohm


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Ok, I have tried with a 0.4ohm coil I just threw together and volatage is worse, 0.5v at 510 slowly climbing?