not what you think!

[Musisoft]

so long ago

I took an electronic-troubleshooting course for domestic audio-video 8 years ago....its so far awar for me too.
A 2 years course and I must ask someone to draw me a shematic.
its pathetic

anyway

thanks to anyone who can help me :wink:

 

[bigal]

Diode Type

Hi, new guy here..

Sorry to ressurect such an old thread :? but i was wondering if anyone gould guide me to a suitable diode for this application. Craigs link takes me to Zenner Diodes, i wanted to clarify this before purchase.. I have a massive stock of 1n4001 diodes, couldent these be used?

thanks for any help, Alex.

 

[jbeng]

Re: Diode Type

... I have a massive stock of 1n4001 diodes, couldent these be used?

The diodes in the schematic are just being used in OR-gate logic configuration. Your 1N4001s should work fine. 1N914, 1N4148 etc. should also work.
JB

 

[bigal]

cool, thanks alot!

 

[bigal]

just to say that i have built and checked this over a lot but have the current fault list that i am still working on...

BOMB TIMER DEBUG LIST
---------------------------------

Output power of NAND gate not sufficiant to drive relay, buffer with BC337 and 2k resistor.

Displays always show 0 [SOLVED - error on schmatic - latch pin must be tied low]

Unable to set timer to less than 9 seconds.

TImer stops (and detonates) at 9 seconds left

Minutes doesnt work (unable to SET but does count via normal abilities)

10 Mins sets in even numbers only but counts from the upper quadrant (EG, you set 20 mins and it shows 20 mins but will start from 30 mins, set 30 mins display shows 20 mins but starts 30 mins... (weirdness...)

any ideas on how to solve any of that lot..

 

[RGBrainbow]

Hi,
hmmm, i wonder if a microcontroller is a solution.
Hook up displays and sensors/traps, some transistors and some software.
Seems to be more flexible and less parts count/PCB space.
regards
joachim

 

[bigal]

for future versions yes, but this is how i have done it, any ideas on how to solve thes issues on this:

Unable to set timer to less than 9 seconds.

TImer stops (and detonates) at 9 seconds left

Minutes doesnt work (unable to SET but does count via normal abilities)

10 Mins sets in even numbers only but counts from the upper quadrant (EG, you set 20 mins and it will start from 30 mins, set 30 mins display shows 20 mins but starts 30 mins... (weirdness...)

sorted the others.. :?

 

[mechie]

Sad but true ...

BigAL
I have my version of this still on breadboard :shock:
Let me check it still works (it's been kicked around in a spare room toy box for ages) and I will try to verify / simulate the faults you report.
I will verify by pm that we are still talking the same circuit.

 

[mechie]

Almost two years and STILL not finished ?

Sorry RGBRainbow while microcontrollers are taking over I don't think they are perfect for everybody and everything.

Hi,
hmmm, i wonder if a microcontroller is a solution.
Hook up displays and sensors/traps, some transistors and some software.
Seems to be more flexible and less parts count/PCB space.
regards
joachim

Maybe a 16F870 would give more scope for 'fiddly bits' but we don't all have the ability to write/program them.
I still find a sense of satisfaction in doing 'proper logic' anyway, real electronics rather than just a bit of assemby laguage in a 'single-chip solution', call me old fashioned but that's what I like.
The original inspiration for this timer was a half-finished circuit on a different forum so the ground rules were kind-of alredy set anyway.

OK, rant over . . . (micro ~#£ing controllers - pah! pass me that EL34).

 

[Nigel Goodwin]

Re: Almost two years and STILL not finished ?

Maybe a 16F870 would give more scope for 'fiddly bits' but we don't all have the ability to write/program them.
I still find a sense of satisfaction in doing 'proper logic' anyway, real electronics rather than just a bit of assemby laguage in a 'single-chip solution', call me old fashioned but that's what I like.
The original inspiration for this timer was a half-finished circuit on a different forum so the ground rules were kind-of alredy set anyway.

It's all really a question of using the 'right tool' for the job, in this case a microcontroller has such massive advantages over doing it with logic chips. It's probably faster to learn to program a PIC than to design, build and test, a hardware logic example to do the job - plus it would be a tiny fraction of the cost and size!.

OK, rant over . . . (micro ~#£ing controllers - pah! pass me that EL34).

Nothing wrong with EL34's, but only in the right place! - you wouldn't want to be doing this project with EL34's and ECC81's :lol:

 

[bigal]

mechie: YGPM

great news there about the breadboard... still fault finding.. :cry:

 

[bigal]

interestingly enough, if you set the 10_mins encoder to 1, the display shows 0000 (2 = 2000 3 = 2000 4 = 4000 5=4000 6 = 6000 etc...) but if you then twiddle the MINS encoder it changes the display to 1100, 1200, 1300, 1400 etc... but when you release the button on 1100 it counts down through 1059, 1058 etc but when you expect it to show 959 it just goes straight to 59 secs. BUT THEN that counts to 0 but then restarts with 59 secs and counts down to 9 then activates the relay... some really wacky logic here.. :?



EDIT:
also, i have just set the 10_MINS encoder to 2, so the display shows 2000, released it (it counts from 2900 down to 2000, when it gets to 2000 it restarts to 2900 and counts to 2000 again and repeats, thus never rreaching anything less than 2000. WTF! :?: :?:

EDIT2: placing the 10 mins on 1 (10 min) gives you 1 min... it counts to 9 then detonates) :x

so weird

 

[bigal]

just though of a reason why mins isnt working unless 10 mins is on something other than 0. the mins 4029 gives an output on pin 7 when it reaches 0 ya? so whats to stop that signal travelling up to the mins 4511 than? but then on the same logic, this would travel right up and hit all of the 4511's..

AHH, but its active low... so i guess i am talking bollo.... never mind... :roll:

 

[mechie]

Re: Almost two years and STILL not finished ?

It's all really a question of using the 'right tool' for the job

I can't argue with you (wouldn't really want to :wink: ) but if you go back to the beginning of this thread you see that Craigey had a circuit already under development - this is basically unchanged but for 'bug-fixes' and 'improvements'. Given that he started by saying he had a little knowledge of circuitry I would dare to suggest that this is the right tool for this job - it was never meant to be compact or 'best practice', just a bomb timer for cadets to play with -and- something Craigey could build.

I would love to try a PIC alternative but lack the reason to write the code just to bin it unused.

BigAl
GYPM ! - I will see if I can do anything tonight, I'm sure my breadboard version of this circuit doesn't have these 'bugs' so could you put the PCB layouts and component overlays on your webpage for me to print out and attempt to trace out? meanwhile I will verify the circuit diagram.

 

[bigal]

sure thing, here is a zip file here with all the stuff in, the PCB files are in circad format and the controller pcb has some other misc stuff on it since i didnt want to waste transparentsies. The zip is password protected, mechie YGPM with the pasword. Dont know if craig want this "open source" yet.. :wink:

neway, thanks for your help so far mechie!

 

[Nigel Goodwin]

Re: Almost two years and STILL not finished ?

It's all really a question of using the 'right tool' for the job

I can't argue with you (wouldn't really want to :wink: ) but if you go back to the beginning of this thread you see that Craigey had a circuit already under development - this is basically unchanged but for 'bug-fixes' and 'improvements'.

From the thread so far, these 'bug-fixes and improvements' include making the device work at all :lol:

 

[mechie]

Functionality is just an improvement ?

Nigel
You have got to agree a working circuit is a BIG improvement on a dead circuit :wink:
(Sorry Graigy1 - slight exaggeration here, the "Acimonious-ZapWizard" circuitry probably did work as a straight 4 digit down-counter - poetic licence applied for - no offence intended to the good guys at the bit-tech.net forums :wink: )

Just for the thread ... the prototype is working again (sad--- two years and I've still got it on protoboards !). BigAl has found a 'typo' on my diagram , I will correct it and mark it clearly as such as soon as everything else is done. I guess one mistake isn't too bad when it's all done in M$Paint from scribbled notes.
Even a microcontroller has some external circuitry -- and a 'debug' phase!

OK - back into my nice comfy padded cell ... mmmm! cosy, warm, quiet!