ESP8266 Regulator issues MCP1825s - Page 1
Forum section: electronics / general

author: giraffe81
author_rank: Newbie
timestamp: February 16, 2016, 01:31:03 pm
content: I am having problems finding a suitable regulator to power a ESP-12E ESP8266 module. I am a beginner to all this, so please bear with me.I have a circuit setup (on a breadboard) to read from a DHT22 and post the result to Thingspeak, this is all running on the ESP8266 using Arduino code. I want to use a lithium 18650 battery as I have had success with these running ATMega328 controllers for months on the same battery. When running my circuit directly from a 18650 battery everything runs fine, the ESP8266 takes a reading, posts over WiFi and sleeps for a minute. However I don't want to run it directly from the battery as it delivers around 4.2V when fully charged which is above the 3.6V max rating (I think) of the ESP8266.Firstly I tried a MCP1700 regulator to power the circuit. No luck, looking at the output over serial the ESP8266 crashes and randomly spits out various errors and memory dumps. I thought this was because the MCP1700 is rated only up to 250mA and I believe the ESP can peak over this when connecting to WiFi.So I move on the MCP1825s - 3.3v rated at 500mA, but I still get the same problem. I have tried putting in a 1000uf cap which seems to allow it to work sometimes, but still way too unstable. Unfortunately I don't have a scope yet, but using a multimeter I can see the voltage out of the regulator drops to about 2.2v (fluctuates) as soon as I try to power up the ESP. It appears that it can't cope, but from reading the specsheet it looks like it should.I also tried using an AMS1117, 3.3V 500mA and it seems to work fine! But this is not suitable for my needs as the quiescent current is way too high to meet my aim of running it off one battery for as long as possible.Any help would be greatly appreciated.

author: TheDirty
author_rank: Frequent Contributor
timestamp: February 16, 2016, 02:08:01 pm
content: These linear regulators all specify specific caps for stability before and after the regulator. Usually .1uf or .01uf located close to the pins.EDIT: Looked at MCP1825s and it's 4.7uf before and 1uf after.

author: giraffe81
author_rank: Newbie
timestamp: February 16, 2016, 03:52:11 pm
content: Forgot to mention I am using suggested caps from the spec sheets. I have 1uf on the output for MCP1825s, nothing on the input, I thought that was optional. Will try your suggestion when I get home.

author: TJ232
author_rank: Frequent Contributor
timestamp: February 17, 2016, 05:04:49 am
content: I have used MCP1825S as a voltage regultor for myESP8266 nEXT EVO Board, especially for the Low Dropout Voltage that is making the board battery friendly for a 1 Li-Ion 4.2V Cell operation. Ci = 10u, Co = 47u, tantalum caps. Don't use less that 10V rated ones.

author: giraffe81
author_rank: Newbie
timestamp: February 17, 2016, 09:21:17 am
content: TJ232, Does Ci mean before the regulator and Co after? 10uf, 47uf seem to be 10x higher that the spec sheet suggests. Did you have similar issues, and had to up the caps to solve it?I tried adding a 1uf on the input, don't have any 4.7uf handy. Although the spec seems to say 1uf-4.7uf on input. Anyway, didn't help for me same issue.I have found a few other people that mention they add a 470uf to the power rail, and also sometimes a small ceramic cap directly across the Vin and Gnd of the ESP8266. I find that adding a large cap, around 1000uf as close to the esp seems to work for me. 470uf does work, but is intermittent. Could this be down to the fact I'm using a breadboard? I have read other posts about resistance of breadboard wires or capacitance of the breadboard.Putting a 1000uf cap in feels like I am just masking a problem rather than solving the issue. I have been debating getting a scope to help with issues such as this, but I don't really know how to use one, and how you would use one to solve problems like this.

author: TJ232
author_rank: Frequent Contributor
timestamp: February 17, 2016, 12:55:23 pm
content: Quote from: giraffe81 on February 17, 2016, 09:21:17 amCi = C InputCo = C outputOn my ESP Board from above link connected to the PC USB port is working OK, with the values from above, no issues to report, more than 6 months run in this configuration. Running also on a Li-Ion 4.2V Cell is OK.If you have a noisy PSU then you can add also a 10-100nF ceramic cap before Ci. The 2$ China-boat Wall-adapters are notorius for very poor regulation and a LOT of noise. Especially if they are the ones over 500mA. 1000uF for Co souns a liitle bit overkill for me.

author: doctormord
author_rank: Regular Contributor
timestamp: February 17, 2016, 12:58:46 pm
content: You have to seperatley look at this problem. First part is your ldo, second is your ESP. In-Ouputcaps are mainly for the control loop of the ldo. The datasheet states what min/max ESR is necessary to have it stable. Going for ceramics would most likely satisfy the control loop.As the ESP is a rather high frequency load, huge capacitances wouldn't improve the situation.I'd go with the values the datasheet states, but keep dc bias in mind. Additionally put a cap of 1/100 in parallel to each for HF.The ESP would need some local decoupling, in the range of capacitance used at the ldo. Low ESR ceramic is the key.Seco

author: TJ232
author_rank: Frequent Contributor
timestamp: February 17, 2016, 01:33:15 pm
content: This is how is looking. Pretty decent I will say. Yellow is input 5V.