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Magic Eye spectrum analyzer

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Im making a spectrum analyzer using 5 magic eye bargraph type tubes.


I want the system to run off of 6 or 12 volts. doesnt matter.

I did a search on this site, and found some stuff on magic eyes, but not sure how to go about wiring a bandpass filter up to them, because I dont think full-wave rectifiers will work, but I dunno.

Also, I googled, and found some steves pages, which had a small 3volt batter powerey amplifier, that uses a transistor, a gate oscillator, and an old filiment transformer as an inverter to supply B+ I was thinking of taking that approach

I got a chicago transformers 6.3v 2amp filiment transformer, and that might do the job.

Any tips, suggestions, comments, idea, schematics?
 
I already got the tubes. And the parts to make an SMPS.

Ok, exactly how much current do I need to run a couple of these magic eyes?

I made a simple SMPS using a 555 timer, an NPN transistor, emitter resistor to burn off the current, and a filiment transformer.


I got 250 to 300 VAC output on the transformer with 12v input. if I increase the frequency, I can get over 1kv output.

But I have no current. none at all. if I try to power a high-speed diode (from a VCR smps) and a filter cap, it kills almost all the output. slowly charges the cap, just like a camera flash. I just cant obtain the current that I might need, then again, I may not need hardly any current at all.



Any ideas?
 
You can simply use a couple of transformers back to back-

i.e. T1: 110V->12V and T2: 110V->6V.

Connect T1 to mains, connect the 12V output to the 6V winding of T2 and you will get 220VAC from the other side of T2. With a diode bridge that would be 1.414 times higher- around 310VDC, so maybe calculate a better fit.

Use decent quality transformers and rectify to a CRC filter to get required voltages. As a bonus you could use the 12V to also power two tube filaments in series.
 
mbates14 said:
I already got the tubes. And the parts to make an SMPS.
Ok, exactly how much current do I need to run a couple of these magic eyes?
I made a simple SMPS using a 555 timer, an NPN transistor, emitter resistor to burn off the current, and a filiment transformer.
I got 250 to 300 VAC output on the transformer with 12v input. if I increase the frequency, I can get over 1kv output.

But I have no current. none at all. if I try to power a high-speed diode (from a VCR smps) and a filter cap, it kills almost all the output. slowly charges the cap, just like a camera flash. I just cant obtain the current that I might need, then again, I may not need hardly any current at all.

Any ideas?

Yup - Do the sums. A 555-based SMPS will typically only be 50% or less efficient. To get 250VDC @ 8mA (5x1.6mA) you have 2W output, so you need 3W input at least. With 12VDC input, you need about 200mA+ on the input side. Your peak current will be much higher, in the region on 1A or more. The output cap MUST be very low ESR else you will never maintain the DC level - a cheap way of doing this is to use several 1uF or 2u2 300V caps in parallel. The diode must be a fast recovery type and the inductor must not saturate.

If you really want to do an SMPS, I can recommend the NEONIXIE-L forum on Yahoo!!!! The files section there has many good designs for SMPSs using 555s and more exotic specialist chips like the MAX1771 - my favourite.

I have a page on a high efficiency MAX1771-based design -
NMdS MAX1771 design - this will give up to 50mA @ 250VDC with close to 90% efficiency. Its a popular design, but be aware - SMPSs are non-trivial to get right - they are all affected by stray capacitance etc. and layout and component choice are critical. The above web page has a lot of information about this.

All in all, for valve use, back-to-back trafos may be easier!

Nick
 
I use my diode from an old VCR smps.


The VCR smps has a Viper50 controller, but i dont think its suitable for useage in a 12v system.

Anyway, I was able, after rectification, and a 100uf at 200v cap. maintain 110vdc with the smps.


if i hook a small tube radio (4 tube type, battery powered) up to the supply, it will sag down to 24 volts. so yea, may need a better design.
 
mbates14 said:
Ive been readin around google a bit.

Basically, I need a 12v to 250v "Boost Converter SMPS"

but most of them use those specialty chips that I dont have.

so i would have to keep it at a transistor level, or use a 555.

Any ideas?

1. Apply to join NEONIXIE-L - Its a moderated forum, like this one. You will be accepted if you behave yourself! Say that Nicko sent you. You should get accepted in a few hours.

2. The designs there are EXACTLY what you are looking for. They have been put together by professional engineers to do exactly what you are after, and use only common, cheap, components.

3. 555 designs are fairly poor generally, whatever you do, but there are several in the files section there that will do the job for you. If you are after something rather better, look at the MAX1771 or MC34063 designs.

4. You do NOT need a "speciality chip" to make a boost converter from 12 -> 250VDC - If you read my page (link in previous message) you will see that at the bottom I give part numbers for Farnell/DigiKey etc. - no part is "exotic" and all cost only a few $.

5. Do not ever, ever, build an SMPS on vero/strip board, or on a plug-in prototyping board. They will perform abysmally, if at all (its all about capacitance). Read the notes on my page carefully - they come from experience!

Nick
 
12V kill 6V secondary?

Probably not. Most plain-jane insulation on transformer secondaries is probably good for at least 50 volts, it wouldn't surprise me to see a wall-wart transformer survive being hooked to 120V for a short time. 12V is really not much potential.

You'd run into problems using a 110V transformer on 220V, but that's a whole different ballgame, even though the proportional difference is the same.
 
Stocker said:
12V kill 6V secondary? Probably not. Most plain-jane insulation on transformer secondaries is probably good for...
You'd run into problems using a 110V transformer on 220V, but that's a whole different ballgame...

SHiFTY said:
Nah, Just use good transformers and it should be fine.

What on earth are you two talking about? Playing pyromaniacs through this forum?!
12V WILL kill either the 12V or the 6V transformer. And not because of the secondary voltage either, and BTW you WOULD be doing exactly the same thing as running a 110V transformer on 220V. The only difference between the primary and secondary is the winding ratio - what is primary and what is secondary is fully notional, the transformer hardly cares. Driving 12V into a 6V winding will result in an overcurrent situation and likely saturation which will overheat them both as it will behave as a (low) resistance during most of the time and not as a transformer.
Whatever next... :rolleyes:
 
For a simple SMPS you might want to look at the UC3843. It is a standard chip, easily obtainable and costs less than 1$. You will also need a few passive components (less than with a 555!) and preferably a high voltage MOSFET (something along the lines of an IRF7xx or 8xx, again easy to get and cheap), and a small ferrite choke. You will probably be able to find this in your scrap VCR SMPS. Alternatively, old CRT monitors (15 inch color, say) are a great source of all sorts of interesting parts like this. You need to cinstruct a simple buck converter. Download the UC3843 or TL3843 datasheet, there is an application schematics in there you can use.
 
I dont have these ICs. Nor do I have a credit card to obtain these ICs.

Im trying to throw something together with what I have in my parts bin.

I got lots of chokes, from mini RF to big 1H chokes. craploads of 2222 transistors, a couple of NPN power transistors, and some power MOSFETS (from car audio IRFZ44).

I got your basic CMOS ICs, 7400 series ICs, and crapload of LM324 and LM741 ICs. some NE5532 ICs.

But these are basic stuff. the ICs you are mentioning are "specialty" to me. I dont have these, need to work with the basics.


I increased the supply voltage on my 555, and its not sagging near as much as it used to. It runs great on my breadboard, and powers a portable tube radio, but shitloads of noise. (to be expected, its AM).
 
not to mention the emitter resistor on the output NPN gets RED HOT within seconds.


Ive got the transformer wired as a collector load to the NPN output transistor (think of an IF stage). and have no resistors, other than a 1k base resistor, and a 10ohm 2watt emitter resistor.

the 555 drives the power transistor directly through the 1k resistor.

Shottkey rectifier on the output with a 100uf at 200v cap.

System will charge to 72 volts unloaded at 12khz. when I turn the radio on, it drops to about 55 to 60.

it was dropping to 24, until I put the 555 circuit from 5v to 12v, and transformer from 5v to 12v.
 
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