ESP8266 Community Forum

- Fri May 31, 2019 2:48 am #82571

What technique do you use to cut off power from the sensors? mossfet?

I understand that you prefer the variation without overload protection, but in case of a short circuit or overload that could damage it, it will burn ... Do you have any protection method to avoid this?

If the sensor has fairly low current requirements (< 5mA) then it is possible to power it directly from a GPIO. I do also use MOSFETS to power sensors or devices where the power requirements are higher. For example I have used them to power sensrs, servos and 433MHz transmitters. I normally use the AO3400 / AO3401 devices as these have low threshold and a low resistance when turned on.

I don't put any extra protection in. I suspect the 400mA current limited version would be OK particularly with decent decoupling but I haven't tried it.

- Mon Jun 03, 2019 9:10 am #82610

What technique do you use to cut off power from the sensors? mossfet?

I understand that you prefer the variation without overload protection, but in case of a short circuit or overload that could damage it, it will burn ... Do you have any protection method to avoid this?

If the sensor has fairly low current requirements (< 5mA) then it is possible to power it directly from a GPIO. I do also use MOSFETS to power sensors or devices where the power requirements are higher. For example I have used them to power sensrs, servos and 433MHz transmitters. I normally use the AO3400 / AO3401 devices as these have low threshold and a low resistance when turned on.

I don't put any extra protection in. I suspect the 400mA current limited version would be OK particularly with decent decoupling but I haven't tried it.

Cool, thanks for the tips.
I'm still analyzing what I'll do.
I'm thinking of a regulator only for the ESP with a drop out too low and another regulator to power the peripherals.
Or two of the same ...
Because the larger have drop currents larger

- Mon Jun 03, 2019 9:44 am #82611

I'm thinking of a regulator only for the ESP with a drop out too low and another regulator to power the peripherals.
Or two of the same ...
Because the larger have drop currents larger

I have previously said that the MCP1700 didn't work reliably for me.
MCP1700:
Range voltage: 6 V Max
Max current out: 250 mA
Quiescent current: 1.6 uA
Drop out voltage: 178 mV

But I have used it in one project with success. I used two in parallel.

I had the layout for that part pattern. I had no space to put in a different part. So I stacked two parts. I filed the top of the first part and then soldered the second one to the lower first part. A hack, but it ended up working well.

Yes the quiescent current is double, but considering how low it is, that didn't seem to be an issue for me. And I end up with the lower drop out voltage. (in theory)

I have not done any detailed measurements with this. I have only been using it. It seems to work, but I would be hesitant to recommend it.

- Mon Jun 03, 2019 1:53 pm #82612

I'm thinking of a regulator only for the ESP with a drop out too low and another regulator to power the peripherals.
Or two of the same ...
Because the larger have drop currents larger

I have previously said that the MCP1700 didn't work reliably for me.
MCP1700:
Range voltage: 6 V Max
Max current out: 250 mA
Quiescent current: 1.6 uA
Drop out voltage: 178 mV

But I have used it in one project with success. I used two in parallel.

I had the layout for that part pattern. I had no space to put in a different part. So I stacked two parts. I filed the top of the first part and then soldered the second one to the lower first part. A hack, but it ended up working well.

Yes the quiescent current is double, but considering how low it is, that didn't seem to be an issue for me. And I end up with the lower drop out voltage. (in theory)

I have not done any detailed measurements with this. I have only been using it. It seems to work, but I would be hesitant to recommend it.

Interesting!
Thanks for sharing your experience!
In this case do you only power the ESP or power other circuits like sensors, LCD, buzzer, leds, etc.?
When you used only one MCP1700 and did not behave well, were you only feeding ESP or had other things together?