User manual

Table Of Contents

Product information28

3.7

Making your own sensors

3.7.1

Overview

Making your own sensors for USB DrDAQ is quite straightforward provided that you

follow these guidelines.

Your own sensors should draw no more than 100mA from the 5V, the

USB DrDAQ is not limited or protected so overcurrents or shorts

could cause damage to the PC USB port.

Designing a USB DrDAQ sensor overview

Each external sensor socket has two channels. One is an auto-detect to inform the

software which type of sensor it is and the other an analogue input that represents the

sensor reading.

There are four pins on the External inputs. This view is looking into the Ext socket on

USB DrDAQ in the direction of entry of the plug:

Pin 1 : Signal Input

Pin 2 : Ground

Pin 3 : Auto Detect

Pin 4 : VCC

Suitable connectors to these external inputs are FCC 68 4/4 plugs.

Alternatively, the USB DrDAQ sensor adapter (break-out box) from Lascells can be

used, part number LA10-716. The pins are clearly labelled on the box.

The range of the Auto Detect and Signal Input voltages must be between 0 and 2.5

volts. This is a hardware limitation and any signals outside this range will not be read

by the unit. Any voltages greater than ± 30 volts fed directly into the device are likely

to damage the unit, and can cause errors with all other USB DrDAQ readings.