Seeking schematics/plans for decimal to binary (microswitch/relay) selector/controller

Jan 25, 2008 3 Replies

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mad.scientist.jr 18 years ago

I am interested in building a "selector" gadget for devices that take jumpers to select a program, such as this game cartridge where you have 5 jumpers to select program #0-31 (the jumpers represent the binary number):

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The selector would have two 7-segment LEDs that display the currently selected program number (0-31), and a couple pushbuttons (+/-) that let you increase/decrease the program #. The device translates the number into binary and turns on/off the appropriate switches or relays which are attached to the jumpers on the device (ie the above game cartridge).

Or I would even like to build a kind of analog to digital converter device which has a potentiometer (for example 100k) which gets translated into an 8-bit number (0-255) and 8 switches get opened/closed that represent the value of the pot. Adding three 7-segment LEDs to display the current value in decimal would be cool and then it could be used as a "selector" as well.

Does anyone know of any plans or schematics out on the Web to construct something like these? (For now I just wire switches to the jumpers.)

Thanks.

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linnix 18 years ago

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Yes, an AVR should work. Your requirements are very similar to our project: Two or Four buttons, 3 digits LCD, 4 channels A2D, runtime current 2mA, power down current 50uA. A button cell battery (CR2032) would last 6 months in power down.

See:

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bill.sloman 18 years ago

Why don't you just use a rotary switch which opens and closes four outputs. You can get binary coded decimal or hexadecimal - if you use a hex switch your users have to understand the the sequence

0,1,2,3,4,5,6,7,8,9,A,B.D,E,F.

Farnell stocks both kinds of switch in a variety of formats, and there must be other broad-line distributors who cater to the segment of the market.

It's a lot easier and cheaper than programming a PIVC and wiring up 7- segment displays.

-- Bill Sloman, Nijmegen

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maxfoo 18 years ago

This would be an easy project using a 8-pin picmiro (12f508,12F629...) pic12f508 cost about a buck at digkey.com You could use a simple momentary-switch to step through from 0-31 If you already have one of the pic progammers found on the web, here's some code to get you started.

cblock count endc

Init clrf count

main

btfsc GPIO,3 ;loop until switch is cleared goto main incf count,f ;increment count by 1 movf count,w ;copy count to Working Register movwf GPIO ;Send Data to OUTput ports xorlw .31 ;check to see if count is 31 btfss status,z ;If so reset back to Init goto Init ;reset count to zero goto main ;if count is not 31 then to main end

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