I was working on a project with Node MCU to control a robot with two wheels connected to yellow motors driven by L298 motor driver module. The motors are powered from two 3.7 lithium ion batteries, the Node MCU are powered through its Vin pin taking its power from 7805 regulator which takes its power from the batteries. I am also connecting a Bluetooth module with the Node MCU in order to have the ability to control the robot using Node MCU connecting it to WiFi or a Bluetooth module,the Bluetooth module takes its 3.3V from Node MCU. Everything was OK right now
I connected a gripper with 2 micro servos Sg90 , each servo takes its power from individual 7805 regulator and they worked fine for 2 days, the third day I tried to power the robot and control it from Node MCU and everything was OK but when I switched to Bluetooth control and disconnected the WiFi as usual, and gave the motors signals to move everything became worse and there were a large noise and disturbance in motor signals and servo signals and the Node MCU indication LED, and the Node MCU became hot for the first time.
I disconnected the Node MCU from the breadboard and connected it through the USB to the laptop and it was OK so I decided to leave it cooling for minutes then I put it again on the breadboard but It didn't give me any indication but it became very hot and the indication LED didn't work and when I connected it back again to USB, the same problem happened and no code can be uploaded and the indication LED wasn't working.
I used my multi-meter on the buzzer mode and put the probes between 3.3V pin and GND pin and awfully the buzzer gave me a sound which means that Node MCU blown out due to a short circuit.
I was wondering what was the cause of this weird thing and how do I overcome this thing the next time
and are there any thing fault in my connection especially the servo motors?
And is there any suggestion for protecting Node MCU from short Circuit?
I wanted to put a diode in series 7805 and Node MCU in order to protect from short circuit or any sudden reverse voltage connection considering that when the voltage coming out from 7805 became 4.3 volt it is OK to power the Node MCU as it has a voltage regulator 3.3 V so is it OK to do that?
Post a schematic diagram of this circuit.
The buzzer (continuity) mode of your multimeter should never be used on a circuit under power. This applies equally to the ohms (resistance) ranges.
As @6v6gtsays, You can't use an Ohm meter, with or without buzzer on a circuit being powered up. Doing that You get false messages from the meter/buzzer but I can't possibly think this measuring caused any damages.
As already requested, attach the wiring diagram and wait. In the mean time You can scratch Your memory searching for any last changes made.
Disconnecting the hot circuitry was definately the best You could do in that situatíon.
Ok. Anyway, don't try to measure Ohm into semiconductor stuff. No harm will be caused but the measurement might be wrong. Try it on a single diode, changing the direction of the diode.
I didn't use the buzzer while powering the circuit
I disconnected the circuit from power and from the breadboard then I used the buzzer
Here is my schematic diagram
Ooops, take it easy now. Looking at the wiring I would urge You to always disconnect the 7.4 volt battories first and then the Node MCU. Starting up I would Power up the Node MCU first and then connect the 7.4 battories.
Be careful! Shorting such battories will blow most diodes and then disaster might strike the rest of the stuff.
I am sorry I don't understand.
The batteries gives 7.4 Volt to 7805 then 5 volt output is powering the Node MCU
so what I do to operate the circuit is putting the batteries and when I want to turn it off, I dicsonnect the battery
The second thing , does this mean that diode will not be a good solution
an if it is not a good solution
Is there any reasonable cause for this short circuit
Okey. Both the Node MCU and the other stuff is powered from the same battory connection.
The short circuit happends when all is powered on. A back current diod might work during a power down sequnce as I was thinking.
Back to square one. Let's see if another helper has better suggestions. Hold out!
