bcd switch info

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mikeb
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bcd switch info

Post by mikeb » Sun Aug 03, 2003 10:00 pm

hello again guys id lie to know if there is anyone that can tell me how the bcd switch works.
the one i have has a switch that capable of accessing the digits 0 thru 9 which i understand to be the bcd code the switch has 6 pins an i havent been able to figure out with an ohm metter exactly wqhat happnes when one of the digits is selected. if anyone can give me info on how these switches work id appreciate it much.

bodgy
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Re: bcd switch info

Post by bodgy » Sun Aug 03, 2003 10:05 pm

Actual layout may differ but often<p>1- -8
C- -C
4- -2<p>C is the common connection tie high or low upto you.<p>The others are the binary weighted number as in 1,2,4,8 .<p>Colin<p>To answer the second part of your question. With an ohmeter put one lead on the common pin and another on pin 1 if you rotate the switch to #1 you should get a short reading or very low ohms, switch to #2 and pin 2 should give a reading, turn again to #3 adn pins 1 and 2 should now give a short/low ohms reading etc.<p>This will not work of course if your BCD switch is opto coupled you'll need to actually plug some voltages into it, but the result would still be the same, just switch the multimeter to volts.<p>[ August 03, 2003: Message edited by: bodgy ]</p>
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rshayes
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Re: bcd switch info

Post by rshayes » Sun Aug 03, 2003 11:23 pm

If this is a thumbwheel switch it could have other codes, but the most likely is BCD. Unfortunately, BCD only requires 5 leads, one common and four leads indicating 1, 2, 4, and 8.<p>A 6 leaded switch may be coded as BCD with complement. In this case, there will be 1 lead that is common for BCD and one lead that is common for the complement. With the switch set to 0, one lead will show no connection and the other five will be connected together. The lead with no connection will be the common lead for the true signal. When the switch is set to 1, There will be a connection between this common lead and one of the other leads. The other four leads will still be connected together. The lead which connected to the common lead will be the 1 lead. By setting the switch to 2, 4, and 8, you should be able to identify these leads. The complement common is the only pin which will never connect to the true common.<p>The common leads may be either at the ends or in the middle, there is no standard pin arrangement.<p>Old thumbwheel switches could have other codes, such as biquinary and excess three. These were very rare compared to BCD and hexadecimal. You probably have BCD.

Chris Foley
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Re: bcd switch info

Post by Chris Foley » Mon Aug 04, 2003 12:54 pm

We'd need more information to be sure, but as it says in a previous post, the extra pin is probably another common or (if it's a large switch or thumbwheel) an inverted common. If it's a six-pin DIP-type with either a screwdriver-adjust slot or a small dial, you might have something like this:<p>http://www.ittcannon.com/media/pdf/catalogs/cd.pdf<p>The .pdf catalog pages explain how BCD switch contacts work. Happy hunting.

mikeb
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Re: bcd switch info

Post by mikeb » Mon Aug 04, 2003 1:02 pm

thanks for the info guys the switch happens to a complimented bcd switch
lead 1 is 1
lead 2 common
lead 3 is 4
lead 4 is 2
lead 5 is common
lead 6 is 8
with each movemrnt of the rotary switsh giving the compliment of the digit shown thanks much for the help

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