Powering 1-Wire devices

Hardware
1

Hi all,

I have been experimenting with using the Imp with 1-Wire devices. I have been using 1-Wire for years and I am very familiar with them.

I notice that the 1-Wire examples, for example that DS18B20 example, leave the device powered constantly. I am building a battery powered device using the MAX31850 and I want to minimize power consumption. Does anyone have experience with parasite powering the devices using strong pullup or powering them using a GPIO pin?

Thanks in advance,

Rob

2

More notes:

I am using and IMP001 with an April board.

The power pin of the DS18B20 is drawing 1.6 µA when supplied from the power pin whether the Imp is running or not.

I connected the power lead and pullup resistor to Pin 9 instead of the power pin and added the following code before the first reset:

`        //raise pin 9 to supply sensor
        hardware.pin9.configure(DIGITAL_OUT)
        hardware.pin9.write(1)
 `

After readings the sensor:

hardware.pin9.write(0)

Things got weird at that stage. The current between Pin 9 and ground was -100 µA. Pin 1 was supplying 3.3 volts and Pin 2 was showing 0.44 V. The power was feeding back through the resistor. Adding ow.disable after reading the sensor made no difference.

The only way of stopping the power at Pins 1 and 2 was to ad this code:

`        ow.disable
        hardware.pin1.configure(DIGITAL_OUT)
        hardware.pin1.write(0)
        hardware.pin2.configure(DIGITAL_OUT)
        hardware.pin2.write(0)`

I have achieved the aim of having no current being drawn when the sensor is not powered. However, it looks pretty inelegant. Does anyone know a better way to do it.

Thanks in advance,

Rob

3

Could you draw the schematic here and post a picture?

4

Hugo - Thanks for the reply and sorry about the delay in replying to your comments. I got dragged away onto other stuff.

My questions are not relevant any more. I have worked out how to use deep sleep, which seems to get the battery life under control.