• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

continuity tester

Status
Not open for further replies.

nitE

New Member
do anyone here know how can i build a continuity tester which can test 100 wires at the same time and the result to be display on a lcd? thank you!
 

Boncuk

New Member
To check 100 wires simultaneously requires a lot of circuitry. If 24 will do you might refer to a kit from ELV (Germany).

Boncuk
 

amitak

New Member
use an MCU with 3line to 8 line decoder circuits to repeatedly scan through the 100 lines
u can check 256 lines using 8 i/o's (configured as outputs)
one more i/o shall act as an input
turn each out put High (or Low) one at a time and then check the high (or low) logic at the input pin.
the display on lcd shall display the result of scan
 

nitE

New Member
Thanks Boncuk.. i try to find that kit you will saying.. as for using MCU.. i cant write program.. i will appeciate if i don't need to use a MCU, i don't mind if the circuit is big.. anyway thanks..
 

amitak

New Member
you can avoid the MCU if u donot need the LCD
use a astable multivibrator to clock the decoders
the return input from scanned lines will drive a speaker (to produce beep)
 

nitE

New Member
look like i had to use a MCU.. its going to be tough i think.. anyway with or without i can't imagine testing 100 wires using 3 to 8 decoder.. i mean how to connect the wires to the decoder..? i will try to think it up
 

ericgibbs

Well-Known Member
Most Helpful Member
look like i had to use a MCU.. its going to be tough i think.. anyway with or without i can't imagine testing 100 wires using 3 to 8 decoder.. i mean how to connect the wires to the decoder..? i will try to think it up
hi,
Do you really mean 'all 100 at the same time' or would sequential testing be acceptable.?

You should also define the test current and voltage required.
 
Last edited:

amitak

New Member
i counted 18 decoders in 2 stages (using 3line to 8 line decoders)
16 decoders in the second stage (16 x 8 = 128 wires can be tested) with the select inputs of all these 16 decoders shorted together
and 2 decoders in first with the select inputs shorted together
so we have 6 select lines - 3 from stage 1 and 3 from stage 2
each decoder in the first stage controls the enable inputs of 8 decoders in the second stage
the enable inputs of the 2 decoders first stage are controlled with i/o lines from the MCU
six more i/o lines are needed three for first stage select inputs (msb) and 3 for second stage select inputs (lsb)
hope it is clear enough - let me know if you need any other details
 

nitE

New Member
hi,
Do you really mean 'all 100 at the same time' or would sequential testing be acceptable.?

You should also define the test current and voltage required.
yes.. it can be sequential.. i don't know about test current or voltage.. any will do.. i supposed.. :rolleyes:
 

nitE

New Member
i counted 18 decoders in 2 stages (using 3line to 8 line decoders)
16 decoders in the second stage (16 x 8 = 128 wires can be tested) with the select inputs of all these 16 decoders shorted together
and 2 decoders in first with the select inputs shorted together
so we have 6 select lines - 3 from stage 1 and 3 from stage 2
each decoder in the first stage controls the enable inputs of 8 decoders in the second stage
the enable inputs of the 2 decoders first stage are controlled with i/o lines from the MCU
six more i/o lines are needed three for first stage select inputs (msb) and 3 for second stage select inputs (lsb)
hope it is clear enough - let me know if you need any other details
ok.. i will try to figure out that..
 

ericgibbs

Well-Known Member
Most Helpful Member
yes.. it can be sequential.. i don't know about test current or voltage.. any will do.. i supposed.. :rolleyes:
hi,
Look at the HEF4514B 1 of 16 decoder ic.:)
 

Boncuk

New Member
Thanks Boncuk.. i try to find that kit you will saying.. as for using MCU.. i cant write program.. i will appeciate if i don't need to use a MCU, i don't mind if the circuit is big.. anyway thanks..
Hi nitE,

I checked ELV home page. They don't offer English. The "Leitungs-Zuordnungs-Tester" LZT-24, part-no. 68-355-81 is not available as a kit. The entire set consists of a transmitter and a receiver. It's priced €49.95

The receiver indicates the numbers of the wires and if they are shorted to any other.

Boncuk
 

nitE

New Member
thanks for your help, Boncuk, i went to that website and found myself unable to understand german but i translet it but i cant find the kit you saying, but i will have to build one myself..

i try to take a look at that 1 to 16 decoder, i suppose it will lesser the circuit size and wiring using that as oppose to the 3 to 8 decoder, thanks Eric

i understand your circuit now, amitak, thanks, it does not seen to be a difficult program to write now, but now i had some problem in writing the result to LCD, i suppose i can use all of PORTB (im using a PIC 16F628) as output from the decoders and one of PORTA as the input and the rest to be the output to LCD? (save for the pin 4 which is the reset) am i right?:confused:

i cant seen to figure out the process in outputing the result to LCD (im reading Nigel's tutorial as of now) trying my best:D
 

ericgibbs

Well-Known Member
Most Helpful Member
hi nitE,
Another handy selector is the HEF4067 analog selector [bi-directional] it can be used with digital signals, useful for 'line state sensing'.
 

Mikebits

Well-Known Member
An FPGA would do the trick. How is your VHDL?
 

nitE

New Member
i got a question to ask.. how can i output a sentences to the LCD if the sentence contain a value from the working register
example: if i want to write "Wire 'w' Pass" and the w is represented by the value 0 to 127

thanks
 

ericgibbs

Well-Known Member
Most Helpful Member
i got a question to ask.. how can i output a sentences to the LCD if the sentence contain a value from the working register
example: if i want to write "Wire 'w' Pass" and the w is represented by the value 0 to 127

thanks
You need to convert the 0 to 127 binary value to ASCII, three characters, then write the value as ASCII to the LCD.
 

Mikebits

Well-Known Member
100 pin cable sounds expensive and huge. Maybe your team should rethink the I/O interface.
 

amitak

New Member
u need 7 lines for the decoder 2^7 = 128
all the return lines will be shorted (only one line for the return path
the lcd can be configured using 6 lines only - 4 data lines, strobe and RS (i ground the read/write pin on lcd to save a data line and provide delay instead of check busy flag)
so u r left with 2 i/o's extra :))
 
Status
Not open for further replies.

EE World Online Articles

Loading
Top