Sensor board w/ liPo charger and fuel gauge +BMP180 +HTU21

[hawk_2050]

@ceech , I recently bought one of the predecessor boards to this new design. I was wondering if you had a better feel yet on likely end user pricing for this new one? Do you plan on populating all active parts, or providing them for users to place themselves? Really looking forward to this board becoming available.

[Sparkman]

@ceech Looks great! When do you expect to have them available for sale?

Cheers
Al

[sj44k]

@ceech Some impressive work you are pulling off here! I am also interested so keep us posted when you have it available !

[ceech]

@lafleur The board is meant to be used with either NRF24l01+, or ESP8266 radio modules. @hawk_2050 The price will be around 14EUR for the version without sensors, and 19EUR for the fully populated one. @Sparkman and @sj44k some boards will be available as soon as next week. Those are the test ones and since everything seem to work excellent, I'll make them available for purchase.

[ceech]

For those interested, here is a link with more detailed description of this board:
http://www.ebay.com/itm/331641400414?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1586.l2649
We will probably offer a bit less complex version here, on mysensors.org.
Enjoy.

[MikeF]

I've just built a version of this, using the solar cell from the Solar Motion Light identified in this project: Solar Powered Mini-Weather Station. I'm using Domoticz as the controller.

I'm trying to understand what the solar and battery currents represent (I had to scale these by 1000, as Domoticz will only display currents in amps). Also, at what battery voltage level will the battery start to charge? and what level of solar voltage is required? I'm also concerned that the solar cell voltage can exceed 6V in bright sunlight - is there a need for overvoltage protection on the LTC4067?

(I'll post details and pics in My Projects shortly.)

[ceech]

Here:

float readVcc() 
{
  signed long resultVcc;
  float resultVccFloat;
  // Read 1.1V reference against AVcc
  ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
  delay(10);                           // Wait for Vref to settle
  ADCSRA |= _BV(ADSC);                 // Convert
  while (bit_is_set(ADCSRA,ADSC));
  resultVcc = ADCL;
  resultVcc |= ADCH<<8;
  resultVcc = 1126400L / resultVcc;    // Back-calculate AVcc in mV
  resultVccFloat = (float) resultVcc / 1000.0; // Convert to Float

  return resultVccFloat;
}

int current = A6;
int chrg = A1;
int cell = A2;
int lipo = A0;
int batterycurrent = A7;

void setup() 
{
  Serial.begin(9600);
}

void loop() 
{
  float napetost = readVcc();

  float tok = ((analogRead(current) * napetost / 1024 ) / 2500) * 1000000; // convert the ADC value to miliamps
  float tokbaterija = ((analogRead(batterycurrent) * napetost / 1024 ) / 2500) * 1000000; // convert the ADC value to miliamps
  float panel = ( analogRead(cell) * napetost / 1024 ) * 2; // measuring input voltage
  float baterija = ( analogRead(lipo) * napetost / 1024 ) * 2; // measuring battery voltage
  int polnjenje = analogRead(chrg);
  
  Serial.print("Vcc = ");
  Serial.print(napetost);
  Serial.println("V");
  delay(400);
  Serial.print("Input current = ");
  Serial.print(tok);
  Serial.println("mA");
  delay(400);
  Serial.print("Charge current = ");
  Serial.print(tokbaterija);
  Serial.println("mA");
  delay(400);
  Serial.print("Solar cell voltage = ");
  Serial.print(panel);
  Serial.println("V");
  delay(400);
  Serial.print("Battery voltage = ");
  Serial.print(baterija);
  Serial.println("V");
  delay(400);
  Serial.print("CHRG = ");
  Serial.println(polnjenje);
  Serial.println("----------------------------");
  delay(2000);
}
/*
Improving accuracy:
To do so, simply measure your Vcc with a voltmeter and with our readVcc() function. Then, replace the constant 1107035L with a new constant:
scale_constant = internal1.1Ref * 1024 * 1000
where
internal1.1Ref = 1,1 * Vcc1 (per voltmeter) / Vcc2 (per readVcc() function)
Example:
For instance, I measure 3,43V from my FTDI, the calculated value of Vref is 1,081V.
So (1,081 x 1000 x 1024) = 1107034,95 or 1107035L rounded up.
Source: http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/
and
https://code.google.com/p/tinkerit/wiki/SecretVoltmeter
*/```

[MikeF]

@Ceech Thanks, I'll give this a try; I need to make some hardware mods first - I'm thinking of including a MOSFET in series with IN, as per datasheet.

[ceech]

@MikeF Sure, if you think it's necessary. OVI pin on the PCB is already connected to input power source. How do you plan to connect the gate of the mosfet to the OVP pin?

[MikeF]

@Ceech I guess I'm concerned that the solar cell voltage Vin might exceed 7V - which the datasheet says is the absolute max. (and the max. overvoltage threshold Vovth is 6.2V). I've been getting >6.5V, with the solar cell not pointing directly at the sun (i.e., not due south / azimuth). I'll take some measurements with the solar cell disconnected. I can see that it would be very difficult to interrupt the IN connection (pin 12); is there another way of limiting the solar cell voltage?

[ceech]

@MikeF Well not limiting, but reducing. Connect one or two ordinary diodes in series with the input, and you will reduce the voltage for 0.7V for every diode.