[neonixie-l] 2 Poisoning questions?

[redrok]

Hi All;

I experimenting with a 24Hr 6 digit Nixie clock. This will have 56 active 
digits and be driven with this transistor matrix operating as a current 
sink.
Question 1:
Of course there can be 60 digits with the 6 Nixies, but only 56 would ever 
be lit.
Or the any Poisoning problems associated with the 56 digits even though 4 
digits will never be active?
Question 2:
This current sink array can only drive 1 digit at a time. So the circuit 
must be multiplexed between the 6 Nixies and drive the digits each with 6 
times the current for 1/6th the time. Do the Nixies have any problems doing 
this? Shorter life? Increased poisoning perhaps?

BTW, the I'm running MicroMite Basic on a 28 pin PIC32MX170F256B processor. 
This is a wonderfull micro a so interactive when testing code.

Thanks!
redrok

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[neonixie-l] Low cost power supplies for bread board use? Here's one... What do you use?

[Robert L]

Hi folks,


A couple people have made recent posts mentioning low cost power supplies 
for bread boarding and bench development. Thought I'd share a supply that 
has been working well for me and see what others may be using as well.


While I have a variety of decent bench supplies, I occasionally want a 
simple and low cost supply that I can dedicate to a given bread board 
project for a period of time… or plywood board in some cases… While I can 
often do without current limiting, excellent load regulation or superior 
low noise, I virtually always want a single power switch. Low cost is nice 
as well...


A case in point requiring +35 VDC, +70 VDC and -210 VDC… all at low current:






Shown above are three Chinese DC-DC Boost converters to the rear under blue 
painter’s tape. These three supplies are run off a single positive 12VDC 
supply with trin-pot adjustable bipolar outputs. Painter's tape? It's a 
bread board and NOT left running unattended! Cautions also apply when 
working with HV... the photo above is not a great example of good bench 
practice! To mitigate, I touch wires only after the supplies are powered 
off, disconnected from the source supply and allowed to discharge for 45 
seconds or so.


Here's one of the three supplies... photo from the web...






The stock specification on these is 8VDC to 32VDC input, +/-45VDC to 
+/-390VDC output. These cost around $6.04/each plus $1.85 shipping… just 
under $20 for three supplies delivered. AND a few weeks waiting for 
delivery. (Suggestion… If these sound good to you, order a few now and save 
yourself the wait when the next project comes round! They take very little 
space in the spare parts file.)


Here’s one of many similar listings for these supplies: 
https://www.ebay.com/itm/322374659518


The careful reader may have noticed that I needed +35VDC for the project 
above and that the supplies are rated for a low end of +/-45VDC… 


I changed the circled resistor below from the stock value of 5.78K to 
28.7K. This dropped the low end output from around 41VDC to 31VDC.


A caution: Please be careful setting high voltage outputs on this modified 
supply as the upper limit has been moved… I marked the modified converter 
for lower voltage and will limit it to around 100V max out. 

I’ve blown similar supplies when running them near their upper limits. As a 
result, I now de-rate these and similar units by at least 10% for both 
voltage and current.


 I saved the original 5.78K/0603 and an 18K/0805 part I tried… These extra 
parts are boxed it the photo below and hung off a large terminal block 
connection for future use if needed.

 





Sooo... What supplies do YOU use?

 

 Best regards,

Bob

 

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