[Sugar-devel] Pulse Sensor: an Open Source Heart-rate Sensor that Rocks by Yury Gitman ? Kickstarter

forster at ozonline.com.au forster at ozonline.com.au
Wed Jul 20 19:41:45 EDT 2011

> Do you know what kind of voltage that mic input can handle? 
> +/5 VDC?

The XO1 is protected at the input by a 5V zener diode. The allowable input is -0.5V to 5V. Inputs outside this range will cause excessive current and damage. Even a single 1.5V battery can cause damage if connected reverse polarity.

The XO1.5 is protected by a resistor,(1/16W 470 ohm SMD0402) and a pair of diodes to ground and to +3.3V which should protect -6V to +9V continuously, and up to higher voltages for shorter periods of time. Similar protection is planned for the XO1.75.

If applying an external voltage to the XO1, it is highly recommended that test leads be made up with a microphone plug and an inbuilt series resistor. 680 ohms is the suggested resistor value, it gives a reasonable input range while still allowing the use of the full resistance range of the XO1.


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