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Author Topic: Is it possible: control Numitron IV-9 with MAX7219CNG LED driver  (Read 1355 times)
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Hello forum
Is it possible to drive six Numitron IV-9 by using one MAX7219CNG LED driver?
- I've already tried the driver with normal 7-segment LED displays with success. Then I tried switching the LED segment with one Numitron, the Numitron gloved dim (getting only 0.5v where it should have had 3.5) regardless of whether the outputs on the LED driver was high or low.

Then I tried adding a NPN transistor (BC337-25) to the output channels of the led driver, to try to drive the Numitrons with the transistor, but also here the numitron gloved dim. (getting only 0.5v where it should have had 3.5)

I calculated the IRES-resistor between pin 18-19 for the led driver by using the lookup table in the datasheet
https://www.sparkfun.com/datasheets/Components/General/COM-09622-MAX7219-MAX7221.pdf

Each segment of the numitron requires 4v and consumes 20mA

I know this is a LED driver, and not designed for bulbs, but shouldn't it be possible to use it anyway? - if no, which driver would you recommend?  - my goal is to use as little pins on the arduino as possible, and therefore i chosen the MAX7219CNG.

If you need any information, please don't hesitate to write  :-)

best regards
Johannes TN
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You would have to use a single MAX7219 for each Nixie tube, with its Scan Limit register set to zero, but in this case you are only permitted to use a segment current of 10 mA, so that is not going to work either.

You cannot (safely) multiplex these tubes.  (You could not multiplex them anyway without diodes)  You need to drive the 22mA continuously to light them.

Forget it.
 
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Damn.. If was sure it would be possible, but little did I know :-)

What about using this one? - then I would have one for each numitron, six in total: TPIC6B595N
http://www.ti.com/lit/ds/slis032a/slis032a.pdf

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That would be fine - really easy to use - you just chain the serial data from one to the next.

Just don't put too much voltage on the poor Nixies!

One thing of course - you don't have to worry about "common anode" or "common cathode" with Nixies.  smiley-grin  You could even run them from AC - presumably using relays!
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Okay, I have some 74H595N shift registers, but I guess those won't work as they have no internal transistor/mosfet to switch the load. If I should use these, I would have to use eksternal transistors/mosfets... (?)

I've never worked with switching higher loads (dc and current more than leds consume), as I am green in working with shift registers. What else would you normally use if you had to switch let's say high power leds or relays with as little pins as possible? As far as I've read so far, most shift registers can't do it... What alternatives do you have then.

Thank you for your helpful answers Paul

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Okay, I have some 74HC595N shift registers, but I guess those won't work as they have no internal transistor/mosfet to switch the load. If I should use these, I would have to use external transistors/mosfets.

Don't!  Just don't!

Get the TPICs and use them.  The current is not that bad really, 140 mA per digit.  (7 transistors per digit is just ridiculous.  Even using both a 74HC5955 and a ULN2008 or whatever for each digit is a bit excessive.)

Shift registers are really easy to use.  I recommend rather than using a library, just using the straight code to drive them; then you will understand what you are doing.
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Fine, I'll go with the TPIC's then :-)
by using one for each I will be able to drive the numitrons without using any other components, right?
- I guess the only thing I would need is a external power supply.

If I have to control high loads (let's say 12v 1A devices) in future, which component would be the best? - do you actually use shift registers like the TPIC's for this, or is there some kind of component primarily for controlling high loads with a small number of pins?

Thank you 
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Actually I got everything up and running using the 74HC595N shift registers I got. Guess I can just use these then?
- I tried using the pineapple library (link https://github.com/Qtechknow/Arduino-Libraries/tree/master/Pineapple) to display numbers on my numitron, but I can't get it going. I either have all the segments lit up nor none of them, I can't turn any segments on individually or anything, even though I know it will work with the shift register as I've tested my shift register using another sketch which is not relying on the pineapple library. Does anyone know how to get the pineapple library to work?
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I thought most TTL ICs are capable of handling 50mA current (sink or source) per output pin?
if you just need 22mA, 74595 should be fine.
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I thought most TTL ICs are capable of handling 50mA current (sink or source) per output pin?
if you just need 22mA, 74595 should be fine.

You clearly thought wrong then!

Take a look at the basic 7400 datasheet.  Note the specifications for low drive as sixteen milliamps, and drive high as 400 microamps.  Short circuit current possibly as high as 55 mA for one output only.
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I thought most TTL ICs are capable of handling 50mA current (sink or source) per output pin?
if you just need 22mA, 74595 should be fine.

You clearly thought wrong then!

Take a look at the basic 7400 datasheet.  Note the specifications for low drive as sixteen milliamps, and drive high as 400 microamps.  Short circuit current possibly as high as 55 mA for one output only.

omg glad my circuit didn't burn.

may have to redesign something = =
thx for pointing out.
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It turns out that HCMOS is actually much more capable than the "original" TTL.
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Does this mean that it's safe for me to use my 74HC595N shift registers to drive my Numitrons? or should I use the TPIC6B595N's I've ordered? - everything seems to run just fine using the 74HC595N's
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Does this mean that it's safe for me to use my 74HC595N shift registers to drive my Numitrons? or should I use the TPIC6B595N's I've ordered? - everything seems to run just fine using the 74HC595N's

What did I state before?
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Hi Guys,

I'm currently looking into the same kind of things. I was wondering how it went in the end and if you could share some of your work or founds?

I first was attracted by Nixies but soon realised that managing 170V wasn't the best for me, and then found the Numitron! There're still cool and the IV-9 seems like the only one working on 3.5V to 4.5V.

Cheers.

ps: +1 Karma for Paul__B
« Last Edit: April 19, 2014, 10:25:18 am by TM » Logged

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