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MisterBill2
- Joined Jan 23, 2018
- 27,563
THANK YOU, J.C!!
I tried to recall the list of reliable suppliers for another thread, and here you come up with it. I appreciate that!! In this case, the 'unintended secondary effects" are helpful.
Latching Off-On pushbutton for portable electronics PCBs
- Thread starter kowshik1729
- Start date
I tried to recall the list of reliable suppliers for another thread, and here you come up with it. I appreciate that!! In this case, the 'unintended secondary effects" are helpful.
MisterBill2
- Joined Jan 23, 2018
- 27,563
In some instances, the simplest solution will be the best. This appears to be one of them.
Hi guys,
I made the below circuit to latch power using push button. The load is a ESP32-S3 MCU, the entire circuit is designed to work in the below manner
Push the button -> The LDO turns on -> ESP32 Turns on -> Immediately a transistor is turned on pulling the MOSFET low keeping the circuit on forever
I have used this button with LED inside it from LCSC as the tactile pushbutton. https://www.lcsc.com/product-detail/Tactile-Switches_Korean-Hroparts-Elec-K6-1212A-04_C128978.html
Here's the problem:
When I press the button, everything is getting powered correctly i.e.,
1. LED inside the button is glowing
2. LDO is getting proper input and output
3. I am seeing 3.3V at the power pins of ESP32.
BUT, the code inside the ESP32 is not running
Alternatively I did another thing, I soldered a jumper wire to the base of the MOSFET seperately and connected it to ground manually. Then everything is working fine, the ESP32 is powering on, the transistor is latching the power correctly the entire system is stable.
What am I doing wrong with this circuit?
I made the below circuit to latch power using push button. The load is a ESP32-S3 MCU, the entire circuit is designed to work in the below manner
Push the button -> The LDO turns on -> ESP32 Turns on -> Immediately a transistor is turned on pulling the MOSFET low keeping the circuit on forever
I have used this button with LED inside it from LCSC as the tactile pushbutton. https://www.lcsc.com/product-detail/Tactile-Switches_Korean-Hroparts-Elec-K6-1212A-04_C128978.html
Here's the problem:
When I press the button, everything is getting powered correctly i.e.,
1. LED inside the button is glowing
2. LDO is getting proper input and output
3. I am seeing 3.3V at the power pins of ESP32.
BUT, the code inside the ESP32 is not running
Alternatively I did another thing, I soldered a jumper wire to the base of the MOSFET seperately and connected it to ground manually. Then everything is working fine, the ESP32 is powering on, the transistor is latching the power correctly the entire system is stable.
What am I doing wrong with this circuit?
Thanks everyone for your answers, i have finally settled for a momentary pushbuttons like this https://www.lcsc.com/product-detail/Tactile-Switches_Korean-Hroparts-Elec-K6-1212A-04_C128978.html
and added a power latch circuitry like this to solve my issue haha
and added a power latch circuitry like this to solve my issue haha
MaxHeadRoom
- Joined Jul 18, 2013
- 30,672
Does it need to be shown earth grounded?
Attachments
Not clear.
Seems odd that the ESP32 is getting power and not operating.
What is the purpose of D3?
What is the PWR_IN voltage?
Measure the voltage at the MOSFET gate when the button is pressed.
Ir may be marginal.
Last edited:
Here's the values -
When button not pressed - 4.65V (Expected because of the 91k ohms pull-up)
when pressed - 80mV (pulling it to ground)
Can you please explain this more? I have done it the same way right? I am using R19 resistor (which I changed to 1k to reduce brightness of LED) to control the LED right? What did you mean by when you told using a seperate resistor please?
Thanks
To block any voltages coming from the MCU, i.e., the DISP_BUTTON net label is connected to the esp32's MCU IO. Do you think I should remove it and try again?
PWR_IN is ~4.8V it's actually USB power.
Looks like the voltages are okay, so don't know what your problem is.
If the button is pulling the gate to 80mV then I don't see why connecting the gate directly to ground should make a difference.
Yes me too, I don't understand why. I had one hunch, the DISP_BUTTON is connected to one of the GPIO pins of the ESP32 as shown below, So do you see any issue of current draw from the MCU?
In my code it looks like I have programmed an internal pull-up and configured this pin as input pin. So would it work if I disable this internal pull-up?
No.
The pull-up is needed to detect a signal high due to D4.
Yes that's right. I have actually got it working but at the risk of losing the GPIO functionality of the button. I simply removed the Diode D4 here at the GPIO pin of ESP32 disconnecting it completely from the power circuit. Now the esp32 is powering on and the code runs.
I believe it's definitely the current draw issue which is causing the problem, but not sure how to fix it keeping the functionality of button and the power latch circuitry.
What is the purpose of relay U7?
Replace D4 with a 10kΩ resistor.
It's basically nothing but a Push button. It has 2 functions
1. During the startup - it works as power latch button
2. once the ESP32 is powered on, it works as a GPIO button.
How would that help please? i can absolutely try this but just wondering what's the difference.
I have replaced it, nothing really happened, same behaviour is seen
Do have a delay in the code that gives time to release the button or code that waits until the release of?
Hmm didn't quite get that, I have a task that keeps looking for the gpio level of the button, so there's enough time to wait for the button to be released. Can you elaborate more please?
