MOD-SIX GPS Repeater

[Jack Buechler]

I have a spare GPS Repeater Version 1 – does any one need one?

 

Let me know

 

 

 

From: <neoni...@googlegroups.com> on behalf of ZY <zongy...@gmail.com>
Reply-To: "neoni...@googlegroups.com" <neoni...@googlegroups.com>
Date: Sunday, 21 August 2016 at 11:09
To: neonixie-l <neoni...@googlegroups.com>
Subject: [neonixie-l] Re: Constant current regulator for Nixies

 

What is your method of current regulation? For example, do you use a PnP transistor or the lm317 method, or something else? I have room to add something for my anodes, but I'm unsure if using a transistor would be accurate.

On Sunday, 14 August 2016 03:02:17 UTC-4, gregebert wrote:

I use current-regulation on my nixie designs, and I've done cathode-side as well as anode-side regulation.  Where you decide to regulate the current depends upon the driver you select. So far, all of my designs use direct-drive (non-multiplexed).

 

My 'Tomorrowland' clock uses HV5532 drivers (it has fourteen IN-18 tubes), so I regulate current on each anode. Yes, there are 14 current regulators.... My wristwatch uses NPN transistors to drive the cathodes, so I regulate the current on each segment.

 

Since 10mA fuses really aren't available, I size the resistor in the current-regulator so that it will operate at about 1/2 it's rated power during normal operation. For example, an 0805 SMT resistor is rated for 1/8 Watt, so I try to design for around 50-60mW. If a gross failure in the regulator occurs, the resistor should overheat and open. I have not tested it, though. I have a fuse on the power supply, and use the smallest value that will handle max operating current.

 

If you really want to be paranoid, monitor all of your anode currents with a multi-channel ADC. I've never done that, but it sounds like a fun project.

 

For cathode current-regulation, you would use an NPN or NMOS transistor; anode-side would use a PNP or PMOS. I found that high-voltage PMOS devices aren't nearly as common as NMOS.

 

If you use MOS devices, I'd recommend a zener-diode across gate-source and also very-high resistors (10Meg +) across drain-source to protect from ESD or unanticipated voltage spikes. It's probably overkill but SMT devices are so cheap and small it's worth the cost to me.

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