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
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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.
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Κυριακή, 7 Ιουνίου 2015

Small metal detector coil made from DVDs

Here is a simple coil for your metal detector.

Things you to need to make the coil.
  • dvds
  • magnet wire of 0.4-0.6 diameter
  • silicon glue gun
  • silicon glue sticks

Coils specs
coil diameter 11.5cm
wire diameter 0.5mm
coil turns 45
core -3 dvds glued together with hot glue

Where to get magnet wire.
safety first
You can buy magnet wire off the internet but plenty can be found in a CRT TV or monitor also.This envolves high risk of electrocution though.If you don't know what you are doing  don't try this.Read the DANGER OF ELECTROCUTION section first.

magnet wire

Magnet wire is hidden in the degaussing coil wrapped around with electrical tape.

There is danger of electric shock involved when opening up a TV. It's capacitors and other component can hold the electrical current off-grid for  a long time.In some cases for months!You need to discharge the TV first before touching anything.IF YOU DO NOT KNOW WHAT YOU ARE DOING DON'T TRY THIS. JUST BY MAGNET WIRE OFF THE NET.

Magnet wire is in the degaussing coil

The degaussing coil in the back of a CRT TV.Danger of electric shock!
silicon glue gun

silicon glue sticks


How to make the coil.
Glue ,say, three dvds together with silicon glue.
Wrapp around the dvds with magnet wire,say for example,45 turns.
Glue the wire.
That's it.

read also
'Pirate'-Russian metal detector
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Παρασκευή, 29 Μαΐου 2015

Trying to restore faded motorcycle case with a heat gun.

My motorcycle case was badly burned by the sun-the color was so faded.

I am trying to restore the case color in this video.I haven't seen this method before used on a motorcycle but I though I 'd give it a try.

The results were good but not excellent.I can see different color patches now on the case.It looks much better now though.
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Τρίτη, 19 Μαΐου 2015

simple 12 volt lead-acid battery charger

Here is a very basic 12 volt battery charger to charge any lead-acid battery small or big.I used what I had to build this except for the transformer . The enclosure is from a broken Pc subwoofer.

When the 12volt battery is fully charged the ammeter should drop significantly which indicates that at this point the battery is nearly full.The battery should measure 13.8 volts at full charge.

This charger produces pulsed DC.

The circuit schematic.

Original schematic found here.

Check the battery specs before connnecting.
You should check the battery specs before connecting it to the charger.There is a chance that the battery will draw too much initial current.In this case you need a current limiter.A simple and very cheap way is to connect a 12volt 10watt car lamp in series with the positive terminal.Like this.

The black lead is connected first and disconnected last.

The battery charging.

Back side of the charger.
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Δευτέρα, 18 Μαΐου 2015

homemade aquarium filter

Very simple to make.

Things you need to make this filter.

  • Plastic bottle,
  • sponge,
  • water filter gravel bought at aquarium and pet store,
  • air pump and... 
  • some pieces of drinking straw cut to pieces (not needed really.I just put them there to float around).
Then I made some holes in the bottle cap-one for the airpump tube and the rest so that the water can get in.Some more holes at the bottom of the bottle for the air to get out.That's it.Pretty simple filter.

read also
Very simple aquarium suspending lighting
Read more ...

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electronics repair made easy