How To "DIY 170vdc Power Supply"

[lemonyx]

Hi All,

Just recently I have stumbled across Nixie Tube Clocks http://www.jogis-roehrenbude.de/Leserbriefe/Nixie-Clock/nixie-clock.htm and **broken link removed**
and now I want to build one or two. Unfortunately these "old" tubes need 170 - 180vdc @2 -3ma to run. I have looked and looked for a power supply that willl not cost an arm and a leg but have not found one yet.

It was mentioned to me You can also use 2 12vac transformers connected back to back. Connect the 12 volt secondaries together. What about caps and diodes? I am an EE dummy but can read, use to draw schematics and design PCB's for a living.

Would someone please point me in the right direction to a site or show me how to do it, I'm sure it's easy

TIA

 

[stevez]

power supply

Look here for a diagram: **broken link removed**

It's a simple bridge rectifier with a capacitor filter.

Let's take a step back. When ac voltages are indicated, the accepted form is RMS unless there is a statement to the contrary. One might also find voltages listed as peak or peak to peak. 120 vac is usually taken to mean 120 v rms. That means it will have a peak value of 1.414 times the rms voltage - for 120 vac that's about 170 volts.

If you were to build the rectifier/capacitor combination with parts of the right ratings, you'd find that voltage across the capacitor would be about 170 vdc if the input to the bridge was about 120 vac. As you add load the capacior won't be able to charge to that value. With 2 or 3 milliamps the voltage might remain high enough for your purposes. That's how you might be able to use 2 - 120/12 transformers back to back to get a trickle of current at nearly 170 volts. DO NOT SKIP THE TRANSFORMERS OR TRANSFORMER - it's tempting but it's not safe.

Please be sure to seek more advise on proper construction of any power supply that uses house current or mains voltage.

Ideally you'd try to find a transfomer with 120 vac primary and maybe 180 vac secondary. I do have several - pulls from old vacuum tube test equipment or radios. Old televisions are another excellent source too but the voltages are much higher.

Good luck.

 

[lemonyx]

Steve

Thank you for your time and the schematic.

So a transformer with 120vac primary and 170-180vdc secondary or higher will work. How do you match the bridge rectifier and cap to the transformer? I would guess the cap would have to be rated at 10,000mf @ 200vdc?

Do you still tie the secondaries together, this would form one output then to the recitfier and the cap would be last? Right?

This is what i have found, prepacked but I'm sure I can make one/two for the cost of this one. https://www.allspectrum.com/store/product_info.php?cPath=26&products_id=169&osCsid=7b3b556cc97a22e504169b6b9caa54dc&sdesc=Nixie+Power+Supply%2C+180v%2C+12ma+Model+%23

The data sheet https://www.allspectrum.com/dc-dc/180vspec.pdf?osCsid=7b3b556cc97a22e504169b6b9caa54dc

This will get me started in the right direction.

thanks again

 

[JimB]

A 10,000uF 200v capacitor is FAR too big ind will be VERY expensive!
Because the current drain is only a few mA, a 200uF capacitor will be plenty.

Transformers. If you have one transformer with a 110/120v primary and a 130/150v secondary, when it is rectified and filtered you will have a 188/200v DC supply. you will not need another transformer.
But if you cant find a transformer with a high voltage secondary, use two 110/120v to 12v transformers.
Connect the 12v secondaries together, then connect one primary to the mains and the other "primary" to the bridge rectifier. That way you have 120v AC which is isolated from the mains. After rectification and smoothing you will have about 170v DC.

JimB

 

[lemonyx]

Great information- thank you

 

[chemelec]

If you build this clock into an Insulated box and use Insulated Controls (assuming there are any controls), there is No Need to even use a transformer. Just use a Full wave Rectifier on the 120 volt line.

Add a current limiting Resistor and a fuse for added protection against Shorts.

 

[Hero999]

I agree you don't need an isolation transformer, as long as you intend on fully insulating all the connections.

How about those of us who live in Europe where the mains is 230V?

Easy, use a transformer with 2 x 115V primaries connected in series for the 5V supply and use the tap in the middle of the primary for the 120VAC suorce.

 

[chemelec]

I agree you don't need an isolation transformer, as long as you intend on fully insulating all the connections.

How about those of us who live in Europe where the mains is 230V?

Easy, use a transformer with 2 x 115V primaries connected in series for the 5V supply and use the tap in the middle of the primary for the 120VAC suorce.

Or Considering the Low Current of about 3 mA, Just use a Resistor Divider to get the 170 Volts. Either Divide the DC Output or Divide the AC Input before rectification.

Two 10K, 5 Watt Resistors should work quite well and they are a lot cheaper than two transformers. They will allow about 11 mA to flow and disipate about 2.5 watts.
That shouldn't run very hot.
Or use Two 15K, 5 watt resistors for Cooler operation.

 

[Hero999]

That might work, but the brightness with change as differant tubes turn on and off.

I wasn't talking about using two transformers, I meant using one 240V transformer with a tap in the primary, you'll probably need a transformer anyway to convert the mains voltage to a lower voltage for the control circuit.

 

[chemelec]

That might work, but the brightness with change as differant tubes turn on and off.

I wasn't talking about using two transformers, I meant using one 240V transformer with a tap in the primary, you'll probably need a transformer anyway to convert the mains voltage to a lower voltage for the control circuit.

Well if you want Regulation, On the DC Output, Use one 10K resistor and a 1N5385B Zener Diode.

Its rated at 5 watts and 170 Volts, +/- 5%

Still far cheaper than a Transformer, Smaller Also.

 

[Hero999]

Still far cheaper than a Transformer, Smaller Also.

True but you don't get me, you probably need a transformet regardless of whether you're using it to power nixies with or not, the control circuit requires a 5V supply which can be supplied from the secondary.