Summary

TWE is more intimate to drive by battery than XBee.

Motive

XBee peak consumption current is more than 100 mA, therefore tough to drive by battery. How is another wireless module TWE? I measued it by my peak current detector. This article has been uploaded at the top page.

要約

TWE のピーク消費電流は XBee と比較すると小さく電池にやさしい。

経緯目的

XBee のピーク電流は 100 mA を越え電池への負担となっていたが，TWE ではどうなのか自作ピーク電流検知器を用いてピーク電流を求める。トップページからの再掲記事です。

I wired and soldered TWE-Lite and I2C temperature sensor module of ADT7410 on the universal board of ICB-88G shown in Photo4. I wanted to know the actual peak current consumption of TWE to estimate battery life. I had made a peak current detector to measure a wireless temperature sensor with XBee before. I used it as before. The photo5 shows the measurement of the peak current.

The peak current detector consist of 0.1Ω resistor, OP amplifier and negative voltage generator power supplied with single +5VDC. The TWE-Lite and ADT7410 were power supplied with my tiny variable voltage regulator. DMM PC510 measured the voltage regulator output. DSO TDS 2002 (CH1 50mV/div, 5ms/div) recorded the peak current shape at single SEQ. The DSO cursor read the peak. The recorded shape of the wave was a twin peak. The bottom time width was always 8ms.

I have programmed that Slip21 shows power supply voltage of TWE-Lite. TWE is the power supply voltage shown in Table3. Ip is calculated current by OP amplifier gain and the detector resistor value.

Conclusion

Varying 2.2 to 3.3V to supply power voltage, The peak current is about 17mA at peak, including constant consumption current 0.22mA. I measured it at 2.8V by PC510. The maximum deviation of PC510 and TWE was 11mV. How does it dissipate consumption current, if monostick fail to power down? I confirmed 4.2mA height and 6ms width pulse at the same period in a few minutes. DSO was CH1 50mV/div and 10ms/div.

In case of XBee, the peak current is about 10mA with successive sharp pulses. the number of the pulses is the same of packet number. The base current is also successive pulses with 40us period.

温度センサモジュール ADT7410 を搭載した状態で，供給電源電圧を変えながら，消費電流を自作ピーク電流検知器により，測定しました。^[1]

ADT7410 の定常消費電流を公開 API により連続動作から，TWE 内部のファームウェアを書き換えて，XBee のように駆動センサをスリープ動作させるのは難しそうです。パワーセービング モードだと比較的簡単に書き換えができるかもしれません。^[2]

1. 入力抵抗0.1Ω電流計特性
2. TWE-Lite + ADT7410