UNI-T UT61E DMM Backlight via sensor control

Описание: This mod based on ability ES51922 chip (the brain of UT61 series DMM's) to control backlight of display.
There where several mods shown here, but many of them are impacts functionality ( some button "reprogrammed" to be a backlight switch) , or exterior of DMM (holes, switches ...)
The goal of my project was is to add backlight control, but not at expense of functionality or drilled DMM's case.
So very simple schematic was build, to implement sensor backlight control. It consist of 2 AMS1117ADJ LDO voltage regulators, 2 PC817 photocouplers , 1 BC337 transistor,
1 Atmel AT42QT1010-TSHR SOT23-6 Capacitance touch controller, several SMT resistors and caps.
The circuit connected to DMM's mine chip via photocoupler, to eliminate any sonic impact on DMMs work.
When I touching the sensor area, AT42QT1010 sends signal to ES51922 chip, and backlight output of ES51922 became high for 60 seconds, or until I touching sensor area second time(within 60seconds).
The purpose of AMS1117: one supplying 5 volt to AT42QT1010, second - connected as current source, to supply 20mA current for led's.
While led's are on, additional current drawn from battery by my cirquit is about 30-35mA.

The schematic can be seen at http://www.diyaudio.com/forums/equipm...