To be clear, there are at least two. First, there is no GND at the power supply, so *none* of the digital and analog signals have a reference potential / return current path / whatever. Second, you show two FET sources connected together (good) but not connected to anything else (bad). Third, there is a high voltage supply that needs to be referenced to the low voltage control circuits.

AND someone is bound to say this - you have a "offline" supply for the nixie tubes - one with no isolation from the AC mains. This is the dictionary picture of lethal.

ak

The Nixie tubes get 170DVC via a rectifier with a cap, it gets 120VAC via a fused input. Not in the drawing.


The 13.6VDC is from a buck converter (top unit), with a 16VAC line in.

 

Finally, we get to the issue I saw when I wrote post #4. As stated by someone else, you would need a separate isolated supply for the gates of each pair of MOSFETs.

 

I think you are correct, I plan on buying the following.

https://www.amazon.com/gp/product/B0CL4853YG/ref=ewc_pr_img_1?smid=A31TID77H4V2UI&psc=1

https://www.amazon.com/gp/product/B0CZLBQX27/ref=ewc_pr_img_2?smid=AC9SQ4GMOJ2Y9&th=1

https://www.amazon.com/CESS-Speaker...98-a1f0-1f34df8479f3&pd_rd_i=B01FX5UNFI&psc=1

Those are not at all similar to the ones that use crimp on terminals. They seem to be a much better quality. I had to examine the detailed drawings to see that part. That type of connectors will work very well. AND they will provide total isolation, as well as not needing any external power supply.Or selector switches.
So the bad news is I do not see how to get the NIXIE tubes involved if you use them, ALTHOUGH the NIXIE tubes can indicate which amplifier you are using.
IS this setup going to be used in a sound systems component sales store ? It seems quite elaborate for a home stereo system.

 

What is limiting the current through the Nixie tubes?

ak

 

I see that those connectors have actual screw clamp connections, not crimp. That makes them repairable. THAT is a serious benefit!!!

 

What is limiting the current through the Nixie tubes?

ak

At this point, nothing. I was thinking a transformer before the rectifier, even a 120v to 115v. Would that work to ensure isolation?

 

I see that those connectors have actual screw clamp connections, not crimp. That makes them repairable. THAT is a serious benefit!!!

Not exactly sure which connectors you are referencing here.

 

Finally, we get to the issue I saw when I wrote post #4. As stated by someone else, you would need a separate isolated supply for the gate of each pair of MOSFETs.

Forgive me, I did not realize you were looking for how the 170VDC was isolated or the lack there of.

 

CAUTION!!! I think that those listings only include the plastic housing, not the actual connection pins and sockets. In addition, given all the information that is not included, I WOULD NOT EVER DEAL WITH THAT SELLER, EVER!!!

Good catch! I will source them elsewhere!

 

At this point, nothing. I was thinking a transformer before the rectifier, even a 120v to 115v. Would that work to ensure isolation?

Isolation - yes. Current limiting - no.

The Nixie datasheet will have upper and lower limits for operating current. With this and the peak voltage out of the supply, you can calculate the resistor value and wattage needed to limit the peak current to a safe value for the device.

ak

 

Isolation - yes. Current limiting - no.

The Nixie datasheet will have upper and lower limits for operating current. With this and the peak voltage out of the supply, you can calculate the resistor value and wattage needed to limit the peak current to a safe value for the device.

ak

I should add that there is a 3 watt 15k resistor coming from the rectifier into the Nixie socket. I was hoping that would limit enough current, does it not? I know Nixies can get cathode poisoning from too much current.

 

If the Nixie "on" voltage is around 60 V, that is a peak current of approx. 7 mA. Check the datasheet.

ak

 

Not exactly sure which connectors you are referencing here.

The ones described in post #25. The one side shows screw clamp connectors.
They actually are much better than what I initially thought. That amazon advertising is really shabby, it leaves out so many valid details. MOSTLY,amazon does that to disguise poor quality products. That series of connectors look like much better products.

 

The ones described in post #25. The one side shows screw clamp connectors.
They actually are much better than what I initially thought. That amazon advertising is really shabby, it leaves out so many valid details. MOSTLY,amazon does that to disguise poor quality products. That series of connectors look like much better products.

Got it!

 

If the Nixie "on" voltage is around 60 V, that is a peak current of approx. 7 mA. Check the datasheet.

ak

These are what I bought - 1N12 new old stock Soviet era tubes.

Numerical Display	0 to 9
Tube Type	Cold-cathode, gas-filled (neon)
Operating Voltage	~170V DC (150V – 180V)
Current per Segment	2.5 mA to 3.5 mA
Warm-Up Time	Instantaneous
Pin Count	13 pins
Anode	Common to all digits
Cathodes	10 cathodes, one for each digit
Tube Life	Up to 20,000 hours
Digit Height	18 mm (0.7 inches)
Diameter	~19 mm
Height (without pins)	~50 mm
Height (with pins)	~60 mm

 

Isolation - yes. Current limiting - no.

The Nixie datasheet will have upper and lower limits for operating current. With this and the peak voltage out of the supply, you can calculate the resistor value and wattage needed to limit the peak current to a safe value for the device.

ak

I would think something like this would do it. I haven't checked my transformer pile, but I don't think I have one.....

https://www.ebay.com/itm/2734406340...8/itun6uoKpN+fWkqFjzq+QQ==|tkp:Bk9SR_qyjOfEZQ

 

What are you using to switch the Nixie cathodes from open-circuit to GND? In this case, GND is the return to the 170 Vdc source.

ak

 

I would think something like this would do it. I haven't checked my transformer pile, but I don't think I have one.....

That works out to 130 mA, more than enough. You still will need one current-limiting resistor per tube, but we don't have an official number for a segment "on" voltage. Rough guess - 36K, 1 W.

First, start with a 100K 1/4 W axial lead resistor. Connect it from the "8" cathode to GND and measure the voltage across it. Repeat for the "1" cathode. This should be a safe way to get some idea of the tube characteristics.

ak

 

Would the CPC1020N 30V, 1.2ADC Single-Pole Normally Open Relay be rated a little too low? Is 1.2A DC too low?

That would allow a max average of 11.5W into an 8Ω speaker load.
It would likely be enough for a typical music listening level, but may not sufficient for loud rock at a party.

 

That works out to 130 mA, more than enough. You still will need one current-limiting resistor per tube, but we don't have an official number for a segment "on" voltage. Rough guess - 36K, 1 W.

First, start with a 100K 1/4 W axial lead resistor. Connect it from the "8" cathode to GND and measure the voltage across it. Repeat for the "1" cathode. This should be a safe way to get some idea of the tube characteristics.

ak

Right now, there is a 3 watt 15k axial resistor on the anode of the tube for current limiting, lights up pretty good.