Here is just another UT61E backlight mod but with a twist. This is the usual obligatory modification for every UT61E owner. :-)
I had this project going for some months but never found the time to finish it. The fact that I had to solder mod wires to the ES51922 was scary enough to stop me every time... Finally I found the courage to do it and here is the finished product:
I've designed the circuit and ended up with the following schematic and components :
Then I placed an order with Elecrow which I highly recommend since they deliver very decent PCBs with the lowest prices.
I started populating the PCB with all the components and then I remembered why SMD work is not my definition of fun... Dimensions of the PCB are 2.7cm x 2cm
Since I had to solder a single wire on the main IC, that was a nice opportunity to modify the factory disabled sleep timer and RS232 functionality as well. Which means two wires...
Nightmare! I almost destroyed the multimeter! I soldered two pins together and couldn't remove the solder, twisted one pin. These pins are extremely fragile! After the proper prayers the mod wires were in place...
The RS232 pin had to be cut from the PCB trace:
Below are some pictures with all the places I needed to connect all the mod wires:
Ground for PCB and LEDs :
Buzzer Pad :
LED wires connected :
LEDs were glued in place with Loctite Super Glue GEL. The LEDs are underneath the wires. (The Gel version is way better than the original.)
RS232 wires and IR phototransistor in place : (You also need to solder an IR Led and a resistor to the supplied serial cable PCB which already has the options but were unpopulated).
Buzzer wire :
Populated PCB piggybacked on the main PCB: You can also see the PCB VCC red wire connected to UT61E V+ which is live only when the unit is switched on.
For the touchpad I used a small piece from a copper sheet 0.12mm :
and below is the finished product :
Power consumption of the piggyback PCB is 30nA when OFF and 8.8mA with both SMD LEDs ON.
Final power consumption of the UT61E now is: 2.38mA in Voltage mode, 2.47mA with RS232 ON, 10.6mA with LEDs ON and 178uA in sleep mode.
All in all I am very satisfied with the upgrade.
The only glitch that it has is, when the backlight is on and you turn the switch only counterclockwise, it might get a false command and turn the backlight off. Maybe this is because I have not shielded the purple wire that runs from the small PCB to the copper touch pad.