Κυριακή, 20 Σεπτεμβρίου 2015

VGA cables not all the same!!

VGA cable pinouts can vary.
"Classic" VGA:
1 Red (Analog) 
2 Green (Analog) 
3 Blue (Analog) 
4 Reserved 
5 Ground
6 Red Return 
7 Green Return
8 Blue Retuen
9 No Connect
10 Ground
11 (ID0) GND (Color)
12 (ID1) NC (Color)
13 Horzontal Sync
14 Vertical Sync 
15 No Connect 

newer standard 

Pin 1 RED Red video
Pin 2 GREEN Green video
Pin 3 BLUE Blue video
Pin 4 N/C Not connected
Pin 5 GND Ground (HSync)
Pin 6 RED_RTN Red return
Pin 7 GREEN_RTN Green return
Pin 8 BLUE_RTN Blue return
Pin 9 +5 V +5 V DC
Pin 10 GND Ground (VSync, DDC)
Pin 11 N/C Not connected
Pin 12 SDA I?C data
Pin 13 HSync Horizontal sync
Pin 14 VSync Vertical sync
Pin 15 SCL I?C clock

Read more ...

Δευτέρα, 7 Σεπτεμβρίου 2015

LED Vu meter circuit (LM3914)

This is a simple LED Vu meter circuit based on the LM3914 IC.

You can use either the LM3914 or the LM3915.The difference between the two is that the LM3914 is analog while the LM3915 is logarithmic.

The input comes for your audio amlifier the speaker out (+ and -).

Feed this circuit with 9 to 12 volts.

Here is the schematic.

And here is an easier way to read the schematic.
Read more ...

Τρίτη, 25 Αυγούστου 2015

Very good variable power supply kit by banggood.

This is a quite good variable power supply kit moneywise and specswise by banggood.It puts out 0-30 volts and 0-3 amps and it costs 10.39 bucks!Not bad at all.

This kit does not include the transformer and heatsinks for the lm7824 and the D1047.

I made little modification though-a 24 volt fan is difficult to come by so I replaced the lm7824 with a lm7812.
Read more ...

Παρασκευή, 7 Αυγούστου 2015

How many volts are needed to light up switch button?

I think one needs 40 volts at least to light up this red switch button.

I usually connect it in series with one of the mains wires (240volts(Danger of electrocution!)).
Read more ...

Πέμπτη, 18 Ιουνίου 2015

TDA2003 stereo amplifier with tone control 20 watts (10+10)

This amplifier is based on this project by construyasuvideorockola.

TDA2003 stereo amplifier
This is a stereo amplifier with two tda2003s..Each channel can put out up to 10 watts. It also comes with tone control operated by a JRC4558 op amp.

The four potentiometers control volume,low frequencies (bass), middle frequencies as well as high frequencies.

Schematic diagrams.

the tone control part

For original schematic more info look at the pdf, page 8.

Volume control noise and other problems

You many have noise when turning the volume control potentiometer due to DC going through it (DC offset).

Τhere are a couple of measures you can take.
  • clean the pot by spraying it with oil (I used what I had-WD 40) and turn it vigorously
  • replace the pot with a better one 
  •  or modify the circuit slightly doing the following
I have found that this can be sold by adding one electrolytic capacitor-10uF- in my cases at the outputs of the 4558 preamp pins 1 and 7.If you add a small capacitor -say 1uF- bass may be cutoff lower.So more bass bigger cap.

All you have to do is replace the 1K resistor at pins 1 and 7 of the 4558 with a 10uF cap.

Here is the modified schematic.

An even more improved version of the circuit.

This is an improved arrangement of the circuit.Some capacitors have been added.The schematics above do not include these additions.

the back side of the pcb

the completed amplifier
Read more ...

Τετάρτη, 17 Ιουνίου 2015

Types of diodes and their symbols.

Diodes come in various types.

We got standard diodes,LED, photo ,Zener,Schottky,tunnel,breakdown as well as capacitative diodes.

Here are their symbols in a schematic diagram.
Read more ...

Recent video


Δεν έχει τον ίδιο αριθμό αναρτήσεων και στα αγγλικά και στα ελληνικά.Ρίξτε μια ματιά και στις δύο γλώσσες.

electronics repair made easy