Arduino mini pro 8mhz 3.3v.
Trying to switch an N-Channel MOSFET (FQP30N06L) to operate bunch of sensors (433 receiver, HM-10, servos etc ...) on a 5v stepped down voltage (S7V8A) from a 8.4 battery input.
What's working ?
I am able to control and switch the MOSFET using pin 11 (digitalWrite HIGH and LOW).
Measuring the lines of the 5V on top gives me indeed 5V and 0V when switched, the led as an indicator being blinking accordingly just fine.
What's not working ?
When switching the MOSFET on and trying to connect a sensor such as HM-10 or a Servo or anything else back to an input pin to read data in arduino (in the picture example of a Temp sensor going back to arduino) the 5V "line" becomes alive as if the mofset is not switching the GND at all (for my understanding it supposed to "cut" the flow in LOW state of any current).
So, MOSFET is OFF and when the Temp sensor is connected to arduino I'm reading around 2.5v on the 5V lines where it supposed to be 0 (since the GND should be "cut") and the led is "half" glowing.
I want the 5v line to off when the mosfet is off so that the sensors connected to it won't get any current.
Trying to debug stuff:
I tried without 5V regulator - same problem - it's something in the current flow that I'm missing here.
Tried resistors in all kind of places (perhaps wrong places) - but nothing helped.
If this helps: I tried to use a 4.2v input source instead of 8.4v - when I did - the problem was gone. infact anything below 5.9v worked, when the MOSFET was switched off , there was no voltage measured on the "5v" lines (it's a stepup/stepdown regulator). Anything above 5.9v input made the 5v lines active after the mosfet was off if a sensor was connected to the arduino.
Hi, @jagden
Welcome to the forum.
Can you please post a circuit diagram of your project?
Label IN your diagram, component numbers, pin labels or numbers and your power supply.
Can you please post a picture(s) of your project?
Sorry but a Fritzy picture does not show the relevant information.
Why aren't the gnd busses on either side of your protoboard joined together?
The busses can't be connected it will "lose" the switch functionality. the "connectivity" goes through the mosfet. I want to switch the GND to be able to turn on and off the whole bus of high voltage sensors.
I do have a P-channel MOSFET, I can expirement with that, however, I think it was hard for me to make it work. Is it more compilcated that an N-Channel one, so you're saying it's prefered in this scenario ? Also, is the diagram correct now ?
They are digital servos who push buttons - they do maintain position. When I enable power to them , they do not twitch or move unless I move them - it's working.
Testing it without a MOSFET will miss the point. The whole problem is the MOSFET when switched off still leaks current if one of the sensors are connected to the arduino.
Okay, well get out a pencil and paper and DRAW your circuit, the diagram in post #3 needs to be sorted out, including putting ALL your hardware parts in it, not plugs and sockets.
You need to draw a circuit that you can follow, current top of diagram to bottom.
Signal form left to right of the diagram.
Use GND symbols instead of trying to show all the gnd wires, it will simplify your schematic and make it easily read.
!!! cool !!!
Yes, there is enough current to hold the 433 receiver from the arudino output. I'm switching it on every 4 seconds to receive a remote push signal and only if i recognize one, I wakeup arduino from sleep. The capacitor near it is relatively new and I haven't implemented it in the real world yet, today it's without this capacitor. I do have a working pcb of the whole project for around 10 month with 4 18650 batteries.
will take some time though:) ....
