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.
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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!)).
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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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