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Topic: IV-18 VFD (Read 1 time) previous topic - next topic

olof_n

Hi!

I have ordered a IV-18 VFD tube and have some questions.

If I understand right I do not need to use current limiting resistors on the anodes and filament?

To drive the tube I will use 2*UDN2981AT and a 4511B to save some pins (MAX6921 is to expensive).
If I drive the anodes with less than 50V it should not be any problem to use UDN2981AT as a driver IC?

/Olof

robtillaart


These kind of questions are often answered in the datasheet of the thingie. Do you have a link?
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Grumpy_Mike

#2
Oct 27, 2012, 07:05 pm Last Edit: Oct 27, 2012, 07:08 pm by Grumpy_Mike Reason: 1
Quote
If I understand right I do not need to use current limiting resistors on the anodes

No it is a gas discharge tube, once it is struck you need something to limit the current so normally that is done by a resistor.

Quote
and filament?

What filaments are there then?

See here for a schematic.
http://www.larsen-b.com/Article/241.html
The driver provides current limiting.

olof_n

#3
Oct 27, 2012, 08:35 pm Last Edit: Oct 28, 2012, 08:10 am by olof_n Reason: 1
Thanks for the answer.

I have read about different IV-18 builds on various sites and they use the MAX6921 driver IC.

I missed that the driver managed the current.

When I look at Adafruit design http://www.ladyada.net/make/icetube/design.html I only see a resistor to pin 1 which is 5V.

What filaments are there then?
Pins 1 and 13 are the filament.

I have found one translated datasheet for IV-18. In the datasheet it stod the following:
Filament voltage: 5V
Filament current: 85mA (typ 75-95mA)
Anode-Grid voltage: 20-30V
Grid Current: 11mA
Total segment Current: 8mA (for one digit)
Anode-Grid current (all segment and digits lit): 25-20mA

I need to drive 8 digits one at a time so the voltage need to be increased.

Maybe it was stupid to skip MAX6921 and order UDN2981AT drivers.
The UDN2981AT was cheap but now I must limit the current with resistors.
8mA total segment current, if I got it right 1mA for one segment (8 segment for 1 digit)?

/Olof

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