Electronics
Contents |
Microcontrollers
Protecting equipment
MOV (Metal Oxyde Varistors) TVS (Transient voltage suppressor) - fastest one
Filters
- CR filter - filter out low frequencies (and DC)
- RC filter - filter out high frequencies
- R(LC) - (R posledovatelno, LC parallel) narrow band rejective filter, filter out all except specific frequencies
- RLC - (out is taken after R before L) - filter out specific frequency
Power systems
Triac, 3Q or HiCom are not vulnerable to noise switching and more robust.
- Battery pulse discharge current (good for lead acid, bad for nimh, ??? for Lithium?)
Power for your microcontroller
Low Dropout Regulator linear regulator (heat dissipation?) 7805
to AVCC resistor 100 ohm, and 0.1 mF capacitor to ground. LC filter on power input (4.7 mF and 47 mkgn)
Driving load on AVR
Darlington transistor array ULN2003 To make more outputs: 74HC595, shift register.
For relays - put direction and protection protection diodes (inductive load).
Checking FET transistors
* For N-type ** Touch black to D, then red to S. It should show around 500mV P-N voltage. ** Touch by red gate (G), then again S. Voltage will be much lower or zero, transistor is open. ** Keep red on S, touch by black now G. Now check black on D, red on S - it should be closed.
Failure on Daewoo LCD TV
Sometimes screen becoming very "green". Looks like unstable contact somewhere. After checking, found instability on LVDS connector on LCD controller board.
There is VCC, PLL and differential pairs. Differential pairs usually clearly visible on PCB - it is thick 0 line (ground?) and negative and positive from both sides of it. You can hook oscilloscope to P - you will see "positive" meander, then next 0 - zero, then "negative", opposite meander.
On my case failure was on first differential pair.
After checking by oscilloscope found difference between "green" and normal, one of differential pairs (negative?) was disappearing.
Checked on main board signal was disappearing too, what clearly shows shortcut of negative line to to 0 line. Cleaning of connector from possible remainings seems made TV to work stable.
