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Topic: Controlling High Voltage 7 Segment Display using MAX7219 (Read 1 time) previous topic - next topic

champ

Hi,
anybody had success with MAX7219 high voltage led configuration [http://www.maximintegrated.com/app-notes/index.mvp/id/1196], can suggest transistor models I can use for Q1, Q2 & Q3, I'm planning to drive digits each having segments rated 9V / 30mA.

Please share the experience on this if anybody allready done this it will be a Great help. 
Thanks. 

BulletMagnet83

Wouldn't the bog-standard BC547 be ok for this? The max. collector current is 100mA and the maximum voltages are more than high enough.

champ

Thanks for the reply, but what about Q2, its a FET ? ... can anybody help me on this..

BulletMagnet83

#3
Nov 07, 2012, 06:30 pm Last Edit: Nov 07, 2012, 06:48 pm by BulletMagnet83 Reason: 1
Looks like a P-Channel MOSFET. I'll bet there's a cheap "standard" one people tend to use for this sort of thing, but I don't have a part number off the top of my head to give you!

EDIT: You could try a parametric search on the component supplier's website of your choice, to find which ones are suited to your requirements :)

champ


Looks like a P-Channel MOSFET. I'll bet there's a cheap "standard" one people tend to use for this sort of thing, but I don't have a part number off the top of my head to give you!

EDIT: You could try a parametric search on the component supplier's website of your choice, to find which ones are suited to your requirements :)


thanks for the info, any possibility of using a digital pot like MCP413 or AD5204, to control the brightness of 7 seg displays  by limiting voltage, instead of PWM ?

BulletMagnet83

I'd just do it in software by sending the appropriate commands to the 7219. Why add extra components and complexity if you don't have to? :)

champ

First thanks for the reply, the problem is I find many threads with problematic situations on this, so I decided go in that way... seems much promising. If you know please provide me some more detailed info about configuration of controlling high voltage 7 segment intensity directly with MAX7219.

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