Jump to content
Electronics-Lab.com Community


Recommended Posts

  • Replies 53
  • Created
  • Last Reply

Top Posters In This Topic

i have spent all day working on the project. at the very last stage of assembling it, i encountered a problem. the inverter input LED doesn't turn ON even if i apply a high to it.. i've traced evferywhere for the fault but found none.. maybe, i'm just too exhausted, so i tried to unwind by playing online games.. i think i'm ok now.. i'll figure out somehow what is wrong..

just a question, one of the LED is not very bright.. it is connected by a foot-long wire. should i shorten it? how about my question about TTL vs CMOS? can they go together in a single circuit?

thanks all for all the help..

Link to comment
Share on other sites

Swap the LEDs. If one side is always dim then the circuit on that side has a problem. Maybe the circuit for the bright side has a problem instead.

TTL and Cmos logic devices are completely different:
1) TTL operates from a 5V supply only. Ordinary Cmos operates with a supply from 3V to 15V or 18V.
2) A TTL input needs a high current to drive it low. An ordinary Cmos output can't supply enough current.
3) A Cmos input needs a fairly high voltage for it to be high. The output voltage of a TTL device doesn't go high enough.                                   

Link to comment
Share on other sites

the problem i encoutered with my inverter was due to the damaged IC.. remember, when i was working on the whistle responder circuit, i used some of the left over parts in making this project.. after i solved the inverter problem, the OR stage malfunctioned.. it's output was always low..

i have solved the problem.. i used the same technique that revealed that my 4081 was defective, since both the 4071 and 4081 have the same pin config, i replaced my 4071 with a 4081. the 4081 worked properly, therefore, the connection was fine. i replaced my 4071 with a new one. it worked fine..

why do ICs gets so easily damaged?

i finished the whole project just in time... i hope my friend will have a good grade.. and i'm pretty confident he would.  8) thanks you guys..

on the other hand, i learned a lot too.. he said the next project they have to pass is an AM radio receiver..

tahnks again for the help..
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...