I want to measurement Battery level.

RE: I want to measurement Battery level.

wojc0008 — Wed, 15 Apr 2015 22:09:40 GMT

Just use a voltage regulator (or an LDO to drop to 3.3V and run them both at 3.3V. If you have the budget available, a switching regulator is a better way to go to run the system at 3.3V.

If it was me, I would parallel the batteries and use a simple boost regulator to drive the LEDs like the TPS61220 (very simple circuit) www.ti.com/.../tps61220

Or an even easier circuit (no inductor, just capacitors), www.ti.com/.../tps60310

Jamie

RE: I want to measurement Battery level.

Stian Røed Hafskjold — Wed, 15 Apr 2015 10:16:45 GMT

5.49 MOhm is too large. You can use lower resistance, but then the battery will be empty really fast. Therefore, you must use a voltage regulator. A voltage regulator INSTEAD of the voltage divider.

RE: I want to measurement Battery level.

GunMin — Wed, 15 Apr 2015 09:58:50 GMT

I use CR2032 Coin cell(3v).

but Working voltage of OLED is 3.3V.

So I Used Two Coin cell.

Would you say that to me 5.49 (Mega Ohm) and 6.71 (Mega Ohm) is unnecessary?

And change to a lower resistance than it is now, I could add a voltage regulator?(In that part)

RE: I want to measurement Battery level.

Stian Røed Hafskjold — Wed, 15 Apr 2015 08:26:37 GMT

Why are you using 6V if both the OLED and the nRF51 are running on 3.3V?
The AIN1 voltage divider is correct.
You can not use a voltage divider to lower the voltage for the VCC of nRF51. You have to use a voltage regulator: en.wikipedia.org/.../Voltage_regulator . Have a look at the 5.49MOhm resistor: 6V / 5.49MOhm = 1.1uA. The resistor is too large to supply enough current to the nRF51. The nRF51 requires at least 16 mA when using the radio. So, you would need to lower the resistor values by a factor of tens of thousands. This would cause the resistors to burn up several mAmps all the time.

RE: I want to measurement Battery level.

GunMin — Wed, 15 Apr 2015 07:25:06 GMT

I tried to configure the circuit again.

I need 3.3V to nRF51822 and OLED.

6V*(6.71M/(5.49M+6.71M)) = 3.3V

If that minimum operating voltage of the OLED is 2.7V,

                             Max    Input        Min     Input
                             3.3V :   6V     =   2.7V :    x

Therefore When the OLED is to use the minimum operating voltage, the input voltage is 4.9V.

      - Maximum voltage:   6V*(2.2M/(2.2M+10M)) = 1.082V
      - Minimum voltage: 4.9V*(2.2M/(2.2M+10M)) = 0.884V
      - ADC value at 6V   - 10 bit setup: 1.082/1.2*1023 = 992
      - ADC value at 4.9V - 10 bit setup: 0.884/1.2*1023 = 754
      - Usable ADC resolution - 10 bit setup: 992-754 = 238

And source are as follows:

#define ADC_REF_VOLTAGE_IN_MILLIVOLTS 1200
#define ADC_PRE_SCALING_COMPENSATION 1
#define DIODE_FWD_VOLT_DROP_MILLIVOLTS 270

#define ADC_RESULT_IN_MILLI_VOLTS(ADC_VALUE)\

    ((((ADC_VALUE) * ADC_REF_VOLTAGE_IN_MILLIVOLTS) / 255) * ADC_PRE_SCALING_COMPENSATION)

static void adc_init(void){	

/* Enable interrupt on ADC sample ready event*/		
NRF_ADC->INTENSET = ADC_INTENSET_END_Msk;   
sd_nvic_SetPriority(ADC_IRQn, NRF_APP_PRIORITY_LOW);  
sd_nvic_EnableIRQ(ADC_IRQn);

NRF_ADC->CONFIG	= (ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos) /* Bits 17..16 : ADC external reference pin selection. */
								| (ADC_CONFIG_PSEL_AnalogInput1<< ADC_CONFIG_PSEL_Pos)					/*!< Use analog input 1 as analog input. */
								| (ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos)							/*!< Use internal 1.2V bandgap voltage as reference for conversion. */
								| (ADC_CONFIG_INPSEL_AnalogInputNoPrescaling<< ADC_CONFIG_INPSEL_Pos) /*!< Analog input specified by PSEL with no prescaling used as input for the conversion. */
								| (ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos);									/*!< 10bit ADC resolution. */ 

/* Enable ADC*/
NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Enabled;	           }

void ADC_IRQHandler(void){
uint8_t     adc_result;
uint16_t    batt_lvl_in_milli_volts;
 int percent;

/* Clear dataready event */
NRF_ADC->EVENTS_END = 0;	

adc_result = (NRF_ADC->RESULT);
batt_lvl_in_milli_volts  = ADC_RESULT_IN_MILLI_VOLTS(adc_result)+DIODE_FWD_VOLT_DROP_MILLIVOLTS;
percent = battery_level_in_pe


NRF_ADC->TASKS_STOP = 1;



//Release the external crystal
sd_clock_hfclk_release();              }

Would not have a problem with as above?

I wonder whether even such a way as above.

RE: I want to measurement Battery level.

Stian Røed Hafskjold — Mon, 13 Apr 2015 13:39:32 GMT

So, you would want to use a voltage divider at the input of the ADC to get as close to 0.6V as possible (Because of minimal current flow in to the ADC). You can check out this post to see how to make a voltage divider: devzone.nordicsemi.com/.../

The post also refers to some example code. Note that this is the voltage going in to one of the ADC input pins on the chip, not the supply voltage (VDD).

For the supply voltage (VDD) you would need to use a voltage regulator in order to lower the voltage to within the operating conditions specified in the nRF51822 Product Specification section 7.

RE: I want to measurement Battery level.

GunMin — Mon, 13 Apr 2015 11:45:34 GMT

Oh.. Sorry, but not yet understood.

If the maximum value of the voltage entering the port is 3.6V and the voltage going to the other device 5V, What is the measurement method?

I have understood the contents as follows:

the voltage entering the board and another device is connected in parallel.
The voltage is put into a board made of 3.6V using a resistor. (Divided by 3.6V and 2.4V.)
If the voltage using the voltage drops, the voltage entering the board and another device (3.6V and 5V) will be the same is that ratio.
Therefore, if I want to know the remaining capacity of the battery, measures the voltage entering the board.

Did I understand the details are correct?

RE: I want to measurement Battery level.

Stian Røed Hafskjold — Mon, 13 Apr 2015 09:08:41 GMT

It is the same question as you posted here right? devzone.nordicsemi.com/.../ Did you read my answer?

RE: I want to measurement Battery level.

Stian Røed Hafskjold — Mon, 13 Apr 2015 09:01:33 GMT

So, you use 6V on the chip? You cannot do that. It is too much. 3.6V is maximum.

RE: I want to measurement Battery level.

GunMin — Mon, 13 Apr 2015 03:40:37 GMT

I put the voltage to VCC_nRF of K1, uses the voltage output to the VTG.

RE: I want to measurement Battery level.

Stian Røed Hafskjold — Fri, 10 Apr 2015 11:50:34 GMT

What is the voltage in to the nRF51?

RE: I want to measurement Battery level.

GunMin — Fri, 10 Apr 2015 09:45:28 GMT

Over time, The battery power level changes rapidly. 970 ~ 960 950 970 980 800 700 800 960 700 600 500 400 500 400 500 ..