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Versione delle 12:27, 23 gen 2019

Would you like to have a speaking multimeter? Maybe it is fancy, but it becomes crucial if you are blind.

I created this project to help a stundent of mine: he is interested in electronics but it is impossible for him to read the values of the components or the measurements in his circuits.

The idea is to connect the multimeter to a linux box or laptop to process its sampling.

UNI-T UT61E does have a choice of serial intefaces: the one usually provided with the device is a RS232 serial interface (unavailable on modern computers). The product list includes a USB cable (UT-D04). Unfortunately it is an IR USB/HID (quite expensive).

Using an infrared sensor (TCST1103, or more precisely half of it), a FTDI board, some wood, and a 1K resistor I built a cheap and useful cable.

The idea is simple: UT61E has an infrared emitter behind, under a protection cover that be removed. The emitter sends a burst of 14 characters every 2 seconds. The signal is 7 bits, odd parity.

I cut the TCTS1103 and kept the phototransistor side. The phototransistor is connected between the RX and GND pins of the FTDI board. A pullup 1K resistor is set between RX and +3.3V. In this prototype I have used a microbot USB to Serial Adapter (MR002-003.2) but I have successfully used other boards (like the very cheap pine64 serial console adapter).

The only tricky part of the building process is to create a slider (a wooden slider in my case) able to keep the phototransistor in front of the emitter.

Ut61circuit.jpeg