The First Devices

At the web page My Personal Story it says that I had passed my electrical engineering certificate in June 1990.

In the end of August 1990 I started doing calculations to construct a mains transformer. The trans-
former consists of electrical sheet metal, coil frames and coils. This device will be a part of a D.C.
power supply and the theoretical power of transformer was 70 VA. In the beginning of October
1990 I cut and formed the electrical sheet metal at a workshop of Lindab Plåtisol in Förslöv.
I was helped by Lindab and also worked 8 months for that company, 1990-91, My Personal Story.
The frame coils were made by cartoon paper and the coils by laquered copper wire. In January'91
the transformer was done. The following two pictures are taken of this device:

Mains transformer Mains transformer

My very first
own constructed

From the front From the upside  

The picture from the upside shows that the sheet metal is not quite closed together. These slacks
cause a buzzing sound while the transformer is working.

Some data

Input:  AC 230 V, 80 VA. Output:  I. AC 25 V, II. AC 7 V

During spring and summer of 1991 I was constructing the D.C. power supply. A direct voltage
will cause the current to flow in only one direction. But of course an alternating current change
direction periodically. The mains transformer, rectifying bridge, glossing capacitors and self-made
PCBs all were assembled in a box of particle boards.

I've taken two pictures of the D.C. power supply:

DC Power Supply 0-30 V DC Power Supply 0-30 V
  A close-up of
the middle PCB

A close-up of
the inside of
the right gable

From the front From the inside  

The right picture doesn't show the old mains transformer. This transformer buzzed too much and
was replaced by two new mains transformers. One of these transformers is assembled on a PCB.

Some data

Input:    AC 230 V, 70 VA
Output:   I. DC 0-30 V, 2 A, Ri = 0.15 ohms,
    II. DC 5 V, 0.4 A, Ri2 = 0.9 ohms

In August 1991 the device was done. After a while the box has been laquered and in December
1998 I improved some of the electronic circuits.

Why do you construct your own DC power supply?
Maybe that's a question of your own. The answer can be something like this:

  • I'm interested
  • It's important to me
  • In general electronic circuits often require direct current

To test electronics you maybe use a
sine wave signal that is generated by
a sine wave oscillator. If this signal
is connected to a loudspeaker, you'll
be able to hear a pure tone.

Directly I continued to construct a
sine wave oscillator. The electronic
circuits were built-in a small box of
particle boards.
  Two cycles of a sine wave signal

In October 1991 the sine wave oscillator was done and I've taken a picture of this device:

Sine Wave Oscillator Some data

Frequency range:    2-82,000 Hz
Voltage amplitude:   0-5 V
Internal resistance:   8 ohms
Power supply:

  AC 230 V,
12 VA, 50 Hz

In June 2000 a reconstruction was done.

At this web page I've described the first three electronic devices of my device story.

As I wrote at "/english" of my home page, I've constructed 50 different devices during the years
1990-2004. After these years I don't count devices anymore.

My Device Story