TC4056 1 cell LiIon charger module

I have a lot of those little boards made around a TP4056 IC.

According to the datasheet:

The TP4056 is a complete constant-current/constant-voltage linear charger for single cell
lithium-ion batteries. Its SOP package and low external component count make the TP4056
ideally suited for portable applications. Furthermore, the TP4056 can work within USB and wall
adapter.
No blocking diode is required due to the internal PMOSFET architecture and have prevent to
negative Charge Current Circuit. Thermal feedback regulates the charge current to limit the die
temperature during high power operation or high ambient temperature. The charge voltage is
fixed at 4.2V, and the charge current can be programmed externally with a single resistor. The
TP4056 automatically terminates the charge cycle when the charge current drops to 1/10th the
programmed value after the final float voltage is reached.
TP4056 Other features include current monitor, under voltage lockout, automatic recharge and
two status pin to indicate charge termination and the presence of an input voltage.

This might be a problem with low capacity cells because to keep the charging in the safe area, the charging current must not exceed 1C (C=designed capacity).

Charging above this might give a temperature rise and this is not good for Li based cells. Of course, there are specific cells that accept charging currents above this safety limit but those are special ones thus not taking risks is a good approach.

Going to the datasheet of the TP4056 give us some interesting informations.

We can conclude that we can use this circuit directly connected to a small Solar panel able to output 6V.

But what about the current? 

Well, the charging current is set by the value of a resistor, Rprog in the test circuit below:

 The value of this resistor determine the charging current as per the table below:

On some modules, the resistor is marked "R3" but anyway, you can easily found it by tracing the circuit from the pin#2 of the IC; in the photo is the one below the little capacitor on the left side of the circuit:

From the factory it came with a 1K resistor which, according to the datasheet, correspond to a 1000mA (1A) charging current.

I changed it with a 2.2 KOhm one and the charging current dropped, as expected, around 500mA.

For final, here is what this module wants to tell us, based on the LED status:

 

Portable GPS barometer UTC Clock

 

Often, in portable I have to use the phone to check for Maidenhead QTH Locator and UTC for logging purposes.

Looking into my junk box I found that i have a lot of ESP based development boards (NodeMCU) and even a uBlox GPS that I bought several years ago and never put it to work.

Also, a small 1.28" SPI TFT was there, waiting...

So, I made a little box usefull for portable/outdoor ham things...

The main feature of this box is to show the UTC and Maidenhead locator as we use this very often into the field but working on this project I thought why not add a barometer and see the pressure.
The next step was to show the evolution of the QNH in time to see if there are some worring variations and a little graph was added.

So, overall, here are the features:

- GPS Coordinates; Lat, Lon, Alt (this need good GPS reception).

- UTC time;

- Maidenhead Locator with 6 symbol precision, good enough for sending it to a correspondent.

- QNH with graphic representation.

- Battery voltage indicator for the LiIon cell.

 The barometric pressure is read at about 15 seconds and averaged for 10 readings then a pixel is drawn on the TFT graph area. For 126 pixels, we will have a history of atmospheric pressure for the last around 45 minutes.

The colours can be easy changed by changing the code.

My little box is powered by one 2000mA LiIon cell which can give around 7 hours of usage. 

The code is available on GitHub.

 

Microphone preamplifier for DC powered (phantom) input

I found this by the grace of FB who reminded me about it (10 years).

A customer came with a specific request: to increase the volume of the headset microphone for his AM Air band transceiver.

If I remember well, it was a ICOM AM transceiver.

The problem was that the space was very small inside that helmet and the second, and bigger, problem was that the microphone had around 8V DC phantom power.

An intervention in the radio itself was excluded because, you know, "life support device" and going inside it was a no-no...

The solution I found was a small preamplifier for both of his headsets (two pilots there).

The schematic:

The PCB was draw by hand. Pretty ugly but it fitted perfectly in the helmet and by using SMD components, the result was very solid: