Any easy way to reduce the output voltage of the Classic Rev6 to 150VDC?

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3 months 1 week ago #13065 by pdoroba
I'd like to use the classic rev 6 clock to drive Pixies.Specifically Burroughs B-9012 Pixies.They require 150V max and 0.004 amps. I know I can just change the values of the limiting resistors to reduce the current but I'm curious about reducing the output voltage of the HV supply. Can this be changed in code?

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3 months 1 week ago - 3 months 1 week ago #13066 by Ty_Eeberfest
Without changing anything you can lower the voltage to 150 using the "menus" accessed by using the pushbutton (but not from the Web interface). Two issues with this technique: 1) 150 is as low as it will go, you'd be running "bottomed out" on the voltage setting, you may or may not care about that 2) If you do Factory Reset the target voltage resets to 180.

A better way might be to alter the code:
BEFORE:

#define HVGEN_TARGET_VOLTAGE_DEFAULT    180
#define HVGEN_TARGET_VOLTAGE_MIN        150
#define HVGEN_TARGET_VOLTAGE_MAX        200

AFTER:

#define HVGEN_TARGET_VOLTAGE_DEFAULT    150
#define HVGEN_TARGET_VOLTAGE_MIN        140
#define HVGEN_TARGET_VOLTAGE_MAX        160

or something along those lines. The HV generator should work okay down to 140 but probably not much lower than that.

Yet another way to do it: Alter the HV feedback voltage divider (R9 and R10). My quick assessment says leave R9 as-is and change R10 to 5500 ohms (5.1K will do if you don't have a 5500 ohm precision resistor), This makes 150V look like 170V to the controller. Should work but the voltage display will be inaccurate, e.g. 150 actual volts will show as 170 "display volts". The idea behind R9/R10 is to make the HV feedback (tagged HVS on schematic) equal 2 volts when the HV is at the target voltage or IOW the controller modulates the HV generator as needed to maintain 2v HVS signal,

EDIT: Schematic here: www.nixieclock.biz/Downloads/C-R6-Schematic.pdf

Look into it later when the dust is clearing off the crater.
Last edit: 3 months 1 week ago by Ty_Eeberfest.
The following user(s) said Thank You: Ian

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3 months 1 week ago #13073 by Ian
I would do the hardware change as well. The software adjustment is only really meant for fine tuning.

Thanks Ty!

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3 months 1 week ago - 3 months 1 week ago #13074 by pdoroba
Thanks for the reply. I found the source code soon after posting and found the lines to modify. I should have looked more thoroughly. :) I'll report back after I've made the required changes and check the output voltage and current.

Edit:

Seems I was replying as Ian was as well. I'll take you both up on the suggestion to swap the feedback resistor and anode resistors.
Last edit: 3 months 1 week ago by pdoroba.

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3 months 1 week ago #13076 by Ty_Eeberfest
When you get it working with Pixies we want PICTURES!! :cheer: Or better yet a short video clip. I think making a Pixie clock out of a Rev.6 is a very cool idea and I'm interested in seeing the outcome.

Look into it later when the dust is clearing off the crater.

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3 months 1 week ago #13077 by pdoroba

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