I cannot make this scheme work

Thread Starter

Grashaa

Joined May 15, 2021
5
Hello I am a high school student of computer engineering and was given an assignment for last grade. I and all my classmates made it inside circuit wizard and its just not working. The scheme that was given to us is kinda old and by professors words 100% functional. I tried changing things but nothing correct happens. Name of this project is literally translated to "testing transistor and diodes with optical induction".
 

Attachments

bertus

Joined Apr 5, 2008
21,364
Hello,

The circuit seems to be a crude transistor tester.
Without a transistor connected, you will get no results.
Try to locate the complete article of the circuit.
It will likely explain how it works.

Bertus
 

ericgibbs

Joined Jan 29, 2010
12,928
hi Grashaa,
Welcome to to AAC.
That translation cannot be correct, all you have is a simple oscillator driving logic gates in order give the 'A' , 'P' letters etc..???
E
I see diodes representing transistor connections.


Update:
Translation 'A' for no connection

ESP_ 268.png
 

Papabravo

Joined Feb 24, 2006
16,159
The circuit consists of an oscillator, some inverters (7405), some NAND gates (7400), and a seven segment display with some steering diodes.
Like in any problem, your strategy should be to divide and conquer.
Start by getting the oscillator to work. It should produce a square wave output at some defined frequency. See if you can discover the frequency and get that to work.
The 7405 Hex inverters have open collector outputs and they won't produce interesting results unless each one has a pullup resistor to +5V

The translation should probably be with "visible indication"
 

MrChips

Joined Oct 2, 2009
23,535
Your 7-segment display shows a connection to GND. That would be true for a common-cathode LED display.
What you need is a common-anode display with the anode connected to positive supply voltage.
 

LesJones

Joined Jan 8, 2017
3,181
I don't see how the display can work. The way the diodes are connected the segment cathodes can only be pulled low so the common anode needs to be connected to a positive supply. There is no positive supply shown connected to the display,
Edit. I see Eric beat me to noticing this problem.
Les.
 

KeithWalker

Joined Jul 10, 2017
1,787
Do any segments of the display light up? There are two types. This one should be the common anode version. The other is common cathode and it will not work in this circuit.
What troubleshooting have you done so far? Is the oscillator running?
 

Thread Starter

Grashaa

Joined May 15, 2021
5
Should be in home work section!
What is this in the original "testing transistor and diodes with optical induction"
"Ispitavalo tranzistora i dioda s optičkom indikacijom" is the original in Bosnian. I've read all of the other replies and I tried everything but Im still stuck. I get the 7seg display to work incorrectly when I reverse diodes and all of the +5V and +0V but on the scheme it clearly says where to turn diodes and stuff. Thank you for all your help I will keep trying.
 

ericgibbs

Joined Jan 29, 2010
12,928
hi G,
Have you tried a Common Anode LED, with the anode to +5v.?
E
Updated image.Screenshot 2021-05-15 183211.png


Added translation.

ESP_ 271.png
 
Last edited:

Thread Starter

Grashaa

Joined May 15, 2021
5
hi G,
Have you tried a Common Anode LED, with the anode to +5v.?
E
Updated image.View attachment 238633


Added translation.

View attachment 238634
[/QUOT
hi G,
Have you tried a Common Anode LED, with the anode to +5v.?
E
Updated image.View attachment 238633


Added translation.

View attachment 238634
UUUUUUU thanks you saved me with that. It works and by instructions it shows an A on display but just for a milisec hmm .
THANK YOU sooo much
and everyone that helped me I learned alot
 
Top