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18650 battery power board

franz-unix last edited by
Hi, to power a sensor or actuator with a 18650 li-ion battery I have designed this pcb based on a tp4056 module and MT3608 booster.

Schematic:

Main features:
- Load sharing circuit to safely power the load while charging the battery
- Boost converter MT3608 (optional) to increase the output voltage. To reduce the size of the board the right part delimited by the vertical white line can be cut out
- Charging status signaling led (optional)
- Voltage dividers (optional) to measure Vin - V batt - V boost - V standby. Output available through J4
- Battery reverse polarity protection through mosfet Q4, excludable through jumper JP3
- Battery voltage measure point can be selected through jumper JP2
This board can be used with this one

I have ordered it (JLCPCB) but yet tested. After that if someone is interested I can share it through openhardware.

Any suggestion / improvement / comment is well appreciated.
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@eiten I haven't yet made any progress on finding a good VOC sensor, but along the way I did find out something interesting regarding CO2: namely, if you sleep with your bedroom door closed at night, then the odds are good that the CO2 levels rise to surprisingly high and unhealthy levels. The better CO2 sensors are factory calibrated and never again need recalibration for the life of the sensor (usually around 10 years or so), because they are used in HVAC systems to control fresh air intake to guarantee indoor air quality. As a for instance, here is one such CO2 sensor: https://www.digikey.com/en/products/detail/senseair/006-0-0008/15790694 At around $50 for just the sensor element itself, it's not exactly cheap, but then again, I'd say it's worth it, because who wants to be burdened by remembering to calibrate their CO2 sensors? Ideally, I'd like to find a sensitive VOC sensor that also will never require calibration. Nearly all, and maybe all, of the off-the-shelf IAQ montoring stuff that you might buy for, say, $300 or less seems to require periodic calibration. For that reason, this might be one of those occasions where build is rather than buy.
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@Tmaster Never assume the original PCB was just a circuit of components, the PCB can incorporate RF shields and antenna radio ground planes...
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It probably has to do with fewer people buying them once summer ends, so companies might lower prices to clear out stock before winter.
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I have success! (oops, that's suppose to be Timer1) I only sample for 1/60 of a second. What I did was to back up all the timer registered I used and then resorted them after I was done sampling. (As opposed to initializing the registers in setup and then starting the timer when needed.) Now I have a Nano sampling the data and sending it to a MySensors Gateway on an RPi3B+ which then sends it to an MQTT broker runing on an old laptop. Also running on the laptop is Home Assistant running inside of VirtualBox. If MySensors does use Timer1, it appears that restoring the registers allows it to be shared. //------------------------------------------------------ISR ISR(TIMER1_OVF_vect){ // interrupt service routine for overflow TCNT1 = TimerPreloadValue; // must be first line! starts the timer counting again digitalWrite(TRIGGER_START_SAMPLE_PIN,HIGH); samplesVolts[--sample]=analogRead(VOLTS_IN_PIN); // decrement before capturing samplesCurrent[sample]=analogRead(CURRENT_IN_PIN); digitalWrite(TRIGGER_START_SAMPLE_PIN,LOW); if (!sample){ // count down to zero digitalWrite(TRIGGER_START_SAMPLE_PERIOD_PIN,LOW); // indicate that sampling is complete samplingEnd = micros(); TCCR1B &= 248; // turns off timer } } //------------------------------------------------------sampleOneCycle void sampleOneCycle(){ // back up timer registers uint8_t TCNT1_b = TCNT1; uint8_t TCCR1B_b = TCCR1B; uint8_t TCCR1A_b = TCCR1A; uint8_t TIMSK1_b = TIMSK1; // configure timer which starts the sampling noInterrupts(); // disable all interrupts TCCR1A = 0; TCCR1B = 0; TCNT1 = TimerPreloadValue; // preload timer //TCCR1B |= (1 << CS10)|(1 << CS12); // 1024 prescaler TCCR1B &= 248; // turns off timer? TIMSK1 |= (1 << TOIE1); // enable timer overflow interrupt ISR // demark sampling sample = NUMBER_OF_SAMPLES; // count down to zero digitalWrite(TRIGGER_START_SAMPLE_PERIOD_PIN,HIGH); samplingStart = micros(); TCNT1 = 65535; // first trigger right away! TCCR1B |= 1; // turns on timer interrupts(); // enable all interrupts // wait for sampling to be complete while(digitalRead(TRIGGER_START_SAMPLE_PERIOD_PIN)){}; samplingEnd = micros(); // restore timer registers TCNT1 = TCNT1_b; TCCR1B = TCCR1B_b; TCCR1A = TCCR1A_b; TIMSK1 = TIMSK1_b; }

18650 battery power board

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18650 battery power board

Suggested Topics

Over the air updates General Discussion • • ToSa

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Does MySensors require Arduino Timer 2? Hardware • mysensors interrupt nano interrupts esp • • OldSurferDude

65Online

11.4kUsers

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Over the air updates
General Discussion • • ToSa

Best VOC sensor for detecting a wide range of VOC's?
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Hardware • • Tmaster

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Hardware • mysensors interrupt nano interrupts esp • • OldSurferDude

65
Online

11.4k
Users

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Topics

112.7k
Posts