ESP8266 Community Forum

- Tue Jun 30, 2015 7:09 am #22052

That step down power supply uses about 15mA - 18mA quiescent current.

Where did you get that number? LM2596 modules will use that much, but the MP2307 datasheet states 1.3mA as typical supply current.

- Tue Jun 30, 2015 7:42 am #22053

That step down power supply uses about 15mA - 18mA quiescent current.

Where did you get that number? LM2596 modules will use that much, but the MP2307 datasheet states 1.3mA as typical supply current.

According to TI datasheet, the quiescent current of the LM2596 is 5 to 10 mA. Which means that neither of these regs is suitable for an ultra-low power sensor application.

I'm using one of the common LM2596 regulators to regulate a 10v wall wart to 5v, then an onboard linear reg to produce 3.3. I fear that no cheap switching reg is going to be clean enough to directly produce the 3.3v needed by the ESP8266, without further filtering.

Last edited by kenn on Tue Jun 30, 2015 8:27 am, edited 2 times in total.

- Tue Jun 30, 2015 7:42 am #22054

If other devices will be powered from the same 6V supply, put a diode in series with the positive IN of the module and a 470 uF cap across the INPUT of the module.

This is exactly my situation. The ws2812b LED strips (80 LED total) are powered from the 6V which is also supplying the buck module. When I gradually turn up the brightness to (estimated) 0.3 amps is when the buck module freaks. (Using 1117 module in its place I can turn up to full, over an amp, no problem). One thought I had was maybe the LED load is imparting some type of ripple waveform onto the buck module.

So I had tried a 100uF cap on input and output to the module and it didn't help. I will certainly try a larger one. I will try the diode too, but what is the thinking there? And it will burn at 1 amp 0.7V * 1A = 0.7 W? (BTW I'm running these off of 4xAAA-- but they only need to last an hour or two!)

Thanks for input from you both!
John

- Tue Jun 30, 2015 3:47 pm #22083 I have both of those step down modules, and quite a few others.
I've had to use/ test all the ones I have for use in low power solar setups for any reliable "real world" data. There is not much English written specs. on those E-bay modules actual performance.
For stepping down 24V-5V for 5V - 3.3V applications using less then 2A I have found the modules I linked to to be the best "real world" performers. And they can take a bit more abuse over the other module.

The diode will prevent the input cap on the module from back feeding into the surge on the 6V supply created by powering on the LED strip.
Also in your case use a 6V supply with more Ah capacity. 4xAA is not enough to fully power 80 WS2812b LEDs.
As 80 LEDs @ .02A (only one color on) is a 1.6A draw not including the loses through the step down module, start mixing colors and you can see the problem.
For 4xAA supply and either step down module 10 LEDs is a "safe" amount. 15 would be my comfortable limit.
20.... Ah what the hell, as long as it works, right?!?! 20 LEDs with all colors on (white) will draw 1.2A. How much capacity does the 4xAA batteries you are using have?