Your first self designed circuit that worked

[goldfist]

I thought it would be neat to start a discussion asking what everyones very first self designed circuit was that worked? This is a circuit that you thought through and used the limited knowledge, limited budget, and tools you had at the time to make it work.

Mine was in 1984 I wanted to make a 10 position rotary switch change a RED 7-segment LED to display 0 through 9. Being just 9 years old this circuit was very crude and later on I found out about the 4511 7-segment Decoder/Display Driver IC which was far less soldering to make it work just having to feed this 4511 a binary input to get the desired output.

My circuit had 47 diodes with the following diode count for each digit displayed.

0 = 6 diodes
1 = 2 diodes
2 = 5 diodes
3 = 5 diodes
4 = 4 diodes
5 = 5 diodes
6 = 5 diodes
7 = 3 diodes
8 = 7 diodes
9 = 5 diodes

At the time I thought it was really cool being just 9 years old and coming up with it on my own using the diodes as 1 way valves for the electrons to the LED segments, and while it worked, there was also some leakage that caused segments that shouldnt be lit to be very dimly lit at times, but you could clearly switch the rotary switch in all 10 positions and watch as it went from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

The application at the time... there really wasnt one, I just wanted to make this circuit and bring it into school and show friends and amaze the teachers of what I did on my own.

The many diodes which may have been 1N4148 or 1N914 's I bought at Radio Shack in packages of 25 i think it was. Back then they use to have a Battery Card in which you could get 1 free battery per month if you brought your card in and they would give you any AAA, AA, C, D, or 9V for free but the other batteries like 6 volt lantern batteries and N etc were excluded. ( I generally went for the D or 9 volt batteries, since I knew that the D batteries lasted longer with higher mA rating, and the 9 volt batteries I could use for circuits 9V or less that were circuits without a heavy battery load.) So I use to get my free battery every month in the 1980s while this program lasted to power my experiments without having to steal so many batteries from my younger brothers toys for portable projects.

 

[KJ6EAD]

I don't remember which was first but I had one of those 75 in 1 lab type kits for a while, built some of the projects in various Forrest Mims books and then started experimenting with the Texas Instruments Complex Sound Generator IC (SN76477N).

Somewhere along the way I started combining blocks of circuit topologies and calculating values but the process is highly derivative so it's hard to say when the 'design' threshold was crossed.

 

[shrtrnd]

I got my start with Olsen Electronics and Radio Shack stores in my neighborhood.
No money in it for stores nowadays I guess, but it was cheap and easy back then.
First one I did myself was a simple transmistter and receiver using infrared diode they
had just come out with. I was very impressed with myself. I could talk into the trans-
mitter, and the infrared devices I picked-up, transmitted to the receiver wirelessly.

 

[goldfist]

The infrared transmitter/receiver reminds me of the lightning detector circuit that was in one of the small radio shack books with use of a phototransistor. I quickly found other neat applications for it since it would hum the 60Hz hum by home lighting especially florescent lights, as well as it was neat to hear the different tones of the remote control when pointed at the phototransistor and you could hear the digital signature of each button.

Later I tried this with a telescope pointing around at the night sky to see if I could pick up anything interesting, but nothing there detected with it that night.

I also hooked the speaker output up to a tape recorder and recorded the digital signature of the buttons of remote and then made a IR transmitter that when the tape was played back it would change channels on the cable box and TV etc ... Played tricks on family members with the Poltergeist VCR, TV, Cable Box around 1990 when leaving the tape recorder out opposite of the devices in clear shot and played the tape which had a 10 minute lead of silence and then the channel changing etc began with my younger brothers trying to figure out how its happening when they have the remotes and my parents yelled my name when the stuff was doing everything just short from dancing in the entertainment center that held them...LOL Later a friend introduced me to this book and I had a laugh through reading it because it reminded me of stuff that I would do as well as did in college which got me into some minor troubles when borrowing stuff from computer lab to classroom lab on projects etc and they thought the stuff was stolen etc and come to find out I was just borrowing it for some experimentation in the lab in which in one situation I had found an older college computer in the hallway laying on its side and decided to bring it to the lab and use its good pieces for troubleshooting a problem with lack of guts to troubleshoot with on my project that was acting up. They just about called the police and my professor asked me where I got the computer parts from and I said there was an old college computer laying on its side by the door that looked like it was trash and so I decided to bring it into the lab and come to find out it works and so I used its guts to find out that I had a bad RAM stick. He then said the college thought it was stolen, so I had to reassemble it and give it back to the college main office and question them why it was by the exit door and looked like junk. From the sounds of it it was brought in by a teacher who went back to their car to get their bags and that is when it vanished and panic set in...OOPS... LOL http://www.amazon.com/Hackers-Computer-Revolution-Anniversary-Edition/dp/1449388396

Sadly though the receiver and transmitter boards were in a box of other stuff from when I made it long ago and it must have accidentally gotten thrown away. But if I wanted to make a new one its a simple circuit to rebuild it again to tinker around with and record and play back digital pulses etc.