Microcontroller driven boost converter

[Tomasz Kowalczyk]

Hi, I'm trying to power my boost converter from a microcontroller and I've encountered stability problems. I tried to make pseudo-PI controller, a PID controller and few other tricks, but the unloaded output just doesn't want to be even close to stable. 

Of course, I'm using a buffer between my MCU and the power mosfet (MCP1407). I run it from 72MHz clock on 100kHz, so PWM has limited resolution (only 720 steps). Of course, having the output voltage match one value of PWM is pretty much impossible, so I accept oscillation of PWM value by 1 as stable output. However, when the load is very light and the output capacitor is smaller than 10uF, the output is hard to control - it tends to oscillate by more than 100 steps, generating over 50Vpp AC wave on the output! This is unacceptable.

The only semi-working method is to reduce my PID controller to only I part with very small gain, which results with settling times of about 0,5s - which for a nixie clock isn't really a big deal. This is a compromise that I was able to achieve. I fear that a converter with so slow reaction will be unable to properly power a multiplexed clock.

I'd like to hear from you - have you tried to power your clocks with MCU driven boost converters? Did you encounter similar problems? Was there any other solution than placing a big cap (increasing "inertia" of the circuit) or pre-loading the output? Or is my PWM resolution just too low and lowering frequency to standard 20-30kHz would do the job?

I really like the idea of using MCU to drive the boost converter, in theory it is perfectly capable of doing the job, I just can't seem to get it to work properly. 

 

[gregebert]

I'm actually using a CPLD (FPGA) for my next project, because the attached RasPi is running Linux and does not have guaranteed response time. It's too risky to have logic controlling something critical, like a DCDC converter, if the behavior is not deterministic at all times. Leaving a transistor on for a few extra microseconds will cause something to burn-up.

Non-critical tasks, such as reading A/D converters, sending status updates to my server, getting & displaying time-of-day, and checking fuses are OK for the RasPi.

I used a CPLD  previously for my wristwatch, and it works nicely.

The logic controlling the DCDC converter will be running at 50Mhz, while most of the other logic on the FPGA will be at 1Mhz.

[Paul Andrews]

Ian Sparkes’ kits use the microcontroller https://www.nixieclock.biz/Store.html . The source code is on Github.

[HuggerMugger]

Suffering for some jetlag and just looking up some stuff on eBay and
AlrExtress I notice that AliX has started selling Nixies. Not sure what the
quality/price are in comparison. Many claim that ICs sold on both places may
be pulled,fake or watever.

I list, just some of the things I find starting with what intrigued me most,
a DC/DC-converter:
https://www.aliexpress.com/item/NCH6100HV-High-Voltage-DC-Power-Supply-Module-For-Nixie-Tube-Glow-Tube-Magic-Eye-dc-12V/32802043085.html

Russian IN-14 tubes (there are surely lot more vendors):
https://www.aliexpress.com/item/FREE-SHIPPING-IN14-Russian-glow-tube-nixie-in14-used-the-tube-is-basically-new/32823956488.html
(Note - "the tube is basically new" .... whatever that means ...
hmmmmmmmm?!)

A few clocks:
https://www.aliexpress.com/item/NB-11-DIY-fluorescent-tube-clock-IV-11-kit-VFD-tube-kit-glow-tube-fluorescent-tube/32776081077.html

https://www.aliexpress.com/item/SMD-original-IV11-fluorescent-tube-clock-DIY-suite-VFD-tube-fluorescent-tube-vacuum-fluorescent-display/32831079652.html

https://www.aliexpress.com/item/FREE-SHIPPING-NB-11-Fluorescent-tubes-clocks-DIY-kits-VFD-tubes-kits-tubes-fluorescent-tubes/32814043066.html

https://www.aliexpress.com/item/FREE-SHIPPING-IV-18-Fluorescent-tube-electronic-tube-clock-Energy-Pillar/32589148961.html

Been buying stuff from AliX för a few years and have to admit that just a
few cheap products have ended up in the bin. Still have some ICs to check
out - just got a packet of ICM7217.

/Magnus

PS. Just got a pair of VFD clock displays from eBay:
https://www.ebay.com/itm/Lot-of-2-IVL2-7-5-IVL-VFD-DIGIT-CLOCK-DISPLAY-TUBE-GREEN-NIXIE-Tube-New/231608379411

And await two clock ICs:
https://www.ebay.com/itm/2x-ic-kr1155nk11-russian-ic-clock-with-4-digit-vfd-display-driver-/191807578854


Stalled projects: http://pastisch.se/tubes/nixie_clocks.htm


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[严泽远]

Please don't fall for the fake one, this seller use my pictures but copy my NCH6100HV power supply with low quality components and wrong parameter.

My NCH6100HV use high quality components(TDK inductor. nichicon high voltage capacitor... ) with gold-plated PCB board, customized connectors with different color, fake one use only gray one...
They print my brand logo and my URL on the board, but they never know what's this module will be used.

Fake one here:

https://www.aliexpress.com/item/NCH6100HV-High-Voltage-DC-Power-Supply-Module-For-Nixie-Tube-Glow-Tube-Magic-Eye-dc-12V/32802043085.html

My website:

http://www.nixieclock.org/?p=1338

New Nixie PSU:

http://www.nixieclock.org/?p=1454

Cheers.

Yan.

在 2017年12月2日星期六 UTC+8下午2:24:01，Soundbrigade写道：

[Tomasz Kowalczyk]

Thanks! I looked into the code and it generally looks similar to my pseudo-PI approach (preloading PWM to some value and then simply ++ or -- if output is too high or too low). I had troubles with slow response, but I think that it was because how analogRead is handled on STM32 hacked to work with Arduino. Also I wasn't calculating new PWM in main loop, but in an interrupt - maybe it was too slow?

I'll copy and paste his code and test it with an oscilloscope, when I find my real Arduino...

[HuggerMugger]

I suspected something like that as some items “looked to be good” to come from the AliX vendors.

 

 

Accidently ran into someone out there selling a kit for the Arduino-run Menta synth (in an Altoids tin can). Thought just Adafruit sold these ....

 

/Magnus

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[HuggerMugger]

Forgot to say thanks for info.

 

I also must state, that I have tow nixie clocks with electronics from PV Electronics and would like to try out the VFD technology.

 

/Magnus

 

From: 严泽远

Sent: Saturday, December 02, 2017 8:11 AM

To: neonixie-l

Subject: [neonixie-l] Re: Nixies on AliX

 

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[Jeff]

Your new VFD clock kit looks great, I just purchased it from your Ebay store.

[John Rehwinkel]

I suspected something like that as some items “looked to be good” to come from the AliX vendors.

 

 

Accidently ran into someone out there selling a kit for the Arduino-run Menta synth (in an Altoids tin can). Thought just Adafruit sold these ....

While there are legitimate AdaFruit resellers (you can buy AdaFruit products from Digi-Key, for example), there is also plenty of counterfeit AdaFruit stuff out there.  They're aware of it, but can't do much about it.

https://makezine.com/2012/04/18/soapbox-counterfeit-open-source-hardware-knock-offs-101/

- John