Your first electronics projects

This is a thread to post about your first electronics projects. I started quite young and my first project was an astable flip-flop using AC128 transistors and 2 light bulbs (I didnt get to use LED's for quite a few years) Then the astable was modified, with one of the bulbs replaced with a small speaker and some component values changed to increase the frequency. Then I made a crude "keyboard" with 8 notes to make an organ with variable resistors attached to each "key" to tune them. The next big project was a radio, all thanks to the Ladybird series of books. I managed to find some pics of the books online with some of the projects.

I had that book

My first real project was a digital speedometer, with the help of Forest Mims Engineers Notebook. Inside a speedometer head there is a spinning cup rotating close to a bar magnet that moves the needle. I drilled 2 holes in that cup for an infrared LED & photo transistor to make pulses that were counted. The 556 timer was calibrated to reset after 60 pulses were counted at 60 MPH. (using mile markers at 1 mile per minute) That number was displayed and held on 2 7segment displays, by the 4511 chips, while the next number of pulses were counted.
In that time frame, if you were going 30 MPH, it would count 30 pulses and display 30.
It worked great until I realized that the 556 timer was temperature sensitive. If I calibrated it on a cool morning, when I drove home on a hot evening, the time base would change and the display would be off by as much as 5 MPH.

I like the construction with the wooden board and woodscrews and domed washers.

When I saw the mounting technique for the ferrite rod antenna, my first thought was "that is not too good, there is great scope for a shorted turn causing a lowering of the inductance".

The first ever thing which I built was a simple audio oscillator form a circuit published in Practical Wireless magazine, way back in about 1962.
I used a "red spot" transistor which probably cost me 7s 6p (37.5p in new money) which was a week and a halfs pocket money at the time.

Some time in the mid 1970s I recreated the circuit to use as a practice oscillator to use while teaching a co-worker morse code.
Digging in the junk box, I find that re-creation:



The schematic looks like this:



JimB

A heathkit valve (tube) stereo amp.. .. (1960 ish)

I was born in 1958 and at age 10 I built a crystal set and, using bed springs as an aerial, listened to the moon landing. I remember being 10 but then found out the moon landing was 1969! However, I was born in September and so my memory is correct.

Mike.