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Help Needed: Burroughs BIP-8806-2 BCD Nixie Tube Decoder/Driver
Posted by ruumoo on 15 Jan, 2018 01:24 -
Hi folks
I have just purchased a beautiful array of 4 Nixie Tubes (plus a + - sign tube), made by Burroughs in England in the 70s.
eBay auction: #263425391032
The main reason for my purchase, other than the incredibly low price, was, that the tubes all come with individual BCD Decoder/Driver circuitry, built into a handy socket with a housing.
I found the corresponding datasheet online and generally got a good grasp, of what's needed to drive these beauties, but It would be awesome if someone else could take a look at the datasheet and confirm/correct my plan of attack, because these decoder/driver Sockets are basically not replaceable.
I have several Question in particular:
How do i drive the decimal point? I didn't understand the section about it's driver requirements.
What does "Cycle time : 200ns" right above the decimal point requiremnts mean?
Do I have to pulse the BCD signal?
I have attached the datasheet, aswell as my drawing of my current understanding (good english)
I wan't to thank anyone who can help me, already in advance
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I took a look. The datasheet is for three possible nixie tubes: 0-9, 0-9 w/decimal pt, +\- sign only.
It has an integrated 4-bit latch and BCD-decimal decoder like a 7441 plus latch, kinda like oddball SN74142 IC, but absent the counter portion. You can hook up a 7490/LM555 counter to it for testing.
There are two possible grounds, one adds a diode-drop. Just use the "normal" ground, pin 7 for TTL levels.
The diode-drop ground does lower current consumption, the IC is a little piggy for power at 90mA 5V.
The decimal point can be driven by an open-collector transistor like MPSA42 with a base resistor.
The BCD inputs have a settling time of 100ns, data there must stable for at least 100ns before a rising edge on the latch command (strobe). Strobe has a minimum of 100ns setup time and pulse 50ns minimum. It's not so much a CLK, but if it was the cycle time is the fastest rate you could update the IC at. -
Awesome, thanks for the quick reply.
Does this mean I could possibly use a basic Square wave clock signal, with a 50% duty cycle with a max frequency of 1Ghz? If not how would I generate the Strobe Signal?
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FWIW I recommend eBay auction: #262524352761 if you don't yet have a power supply. Comes in a sweet LASER cut box
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would this be an working circuit?
I'm new to Eagle, so excuse the crappy circuit diagram
the strobe input is not yet connected, as I don't yet know how to generate it.
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Can't you just drive them direct... i.e. parallel the BCD inputs and have a line for each strobe?
Also add Rs on the bases of the Transistors. -
good idea, but how would I do that?
Oh yeah, thanks for reminding me of the r's, I forgot thaem in the heat of learning Eagle
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Instead, consider making a bus with the four BCD data lines. All are tied together, all digits and the MCU. This is 4 MCU pins.
To select a digit to latch, use a 'LS138 3-line to 8-line decoder, connecting to each digit's strobe line. This is 3 MCU pins.
You would output the BCD data (one digit) from the MCU on the bus, then toggle the desired digit's strobe by writing to the 'LS138.
This is fewer IC's and fewer MCU pins. -
good idea! but doesn't the decoder need to be non inverting? with an ls138 i could only set one pin low, but to latch i need to set the pin high
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The nixie module strobe line is usually high, and pulsed low to latch BCD data on the strobe's rising edge.
At idle, you give 000 to the 'LS138 (which has inverted outputs), so only Y0 is low, and not connected to anything.
To update a digit, output digit 1 BCD data, and then send the '138 a 001 to assert Y1 low, and write back 000 to finish (latch).
Y1 to digit 1, Y2 to digit 2 etc. You could add a latch IC for the decimal points if you need to use fewer pins on the MCU. -
Got the to work without blowing anything up
Gonna post some pictures when its done