Variable frequency variable pulse width neon oscillator

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

Hi..

I've tried building this funky little oscillator. Unfortunatly the neon's I have are rated for 200 V.. So it's not working..

So I would like to scale this up to 220 V. instead of 125 V. Is this a matter of just using higher wattage resistors ? Or should values be doubled aswell ? Also how many Watt's should the 24 K. and 1 K. resistors be ? 10? or more ?

Thank you..

Schematic is from this book http://www.tuberadios.com/ge.zip

neon osc.JPG

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andrewF · Posted: Fri May 08, 2009 11:48 pm Post subject:

There are very few neons that have such a high breakdown voltage. What kind are they?
maybe too much hassle unless they look good Smile

i suggest it would be easier to just get some ne2 bulbs, they are the most common and only cost a few cents each.

Neons only use a few mA...usually less than 2mA. If you do go the over 200V route, it may be better to use 1/2W resistors and caps rated for 300 or more V.
if you use ne2 bulbs and 125V, regular 1/4W resistors should be fine.

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

I don't know what type they are but there cute.. Are you sure ? The 24 and 1 K. Are directly in the path from 125V. to gnd.. Wouldn't they just "explode.."

andrewF · Posted: Sat May 09, 2009 4:36 am Post subject:

Yep

they will enjoy ~0.6W, just went and had a look at some of my neon ccts, mostly use 0.6W metal film resistors.
resistors won't explode, unless you do something really vicious to them, generally just start to brown, then smoke...then smoke a lot more.
Caps tho are far more entertaining

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

So 1watt resistors should be ok? Well I've had 3 watts resistors explode on me. And yes I mean explode..

Anyway's I built it.. Again.. And again.. It just keeps blowing fuses.. It's pissing me off..

andrewF · Posted: Sat May 09, 2009 5:46 am Post subject:

exploding 3W Shocked

I'm jealous, never managed to do that

1W will do

but I wonder why the fuses keep blowing??

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

Yup it was really loud like a serious sized firecracker..

I don't know either.. I'm using a light dimmer to go from 220 to 120 V. It shouldn't be a problem no..? Oh I just noticed the capacitor should be elecrolytic.. Damn.. I've been using ceramics. This might be why ?

blue hell · Posted: Sat May 09, 2009 7:00 am Post subject:

andrewF · Posted: Sat May 09, 2009 7:18 am Post subject:

a light dimmer is generally not a voltage divider circuit, it operates quite differently - usually they have a couple of SCRs (silicon controlled rectifiers) in there.
I don't think it is a good power source...especially if you are just running it direct from the mains supply.

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

Which diode are you using? Which part #, I mean .... ?

blue hell · Posted: Sat May 09, 2009 8:20 am Post subject:

No filter cap?

And it being connected directly to the mains is not really a feature for an audio circuit ... you didn't connect it up to your audio or computer equipment I hope ... this could be lethal ...

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

JovianPyx · Posted: Sat May 09, 2009 9:04 am Post subject:

Gotta agree with "dangerous"... While these circuits are a curious novelty, there's really nothing sonically wonderful about them. I believe that there were some old organs that used neons for dividers (I've got a circuit for that somewhere), but with the plethora of low voltage parts available now, there seems to be no reason to do this kind of thing. Neon oscillators are more difficult to control and don't interface easily with other synth circuits (transistor stuff). A neon oscillator that responds accurately to a pitch CV will be difficult to design. The biggest let down for me when I did similar experiments years ago is that at audio frequencies, the neon lamp looks like it's just "on" all the time. The only surviving neon circuit I have is a game machine made of 2 stepping relays and some DPDT relays. It played the game of "Nim" or "Black Match" and has (believe it or not) a clock circuit (very low frequency) built from an NE-2 lamp. The UI is a panel with 21 NE-2 lamps. It works, but I never liked working on it because everything in it needs 120 volts. TTL ICs and LEDs would have worked better and would be a lot safer... Shocked

Of my own "Oh Krap!" episodes, I built a power supply (for vacuum tubes) and put the filter cap in backwards. Somehow I was smart enough to power it up using a LONG extension cord. BOOM! Then there was the time I tried to light up an NE-2 without a limiting resistor. That went off like a single ball roman candle... Best not to do those things.

If you're looking for novel sound generating circuits, look for UJT relaxation oscillators (for something really simple) or look up "crackle box".

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

richardc64 · Posted: Sat May 09, 2009 9:57 am Post subject:

YOU ARE TEMPTING FATE.

There's no value in this, except maybe to see how long you can push your luck.

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

horchacha · Joined: Sep 05, 2007 Posts: 8 Location: tucson, az

hey - so i re-read the tread a few times to get an idea of whats going on.
are you seriously using 220V EU mains through a dimmer to lower the voltage? never do that again.

if you want to play around with these circuits - the most important aspect is the power supply. you need to isolate it from mains (you ever heard mains voltage through a amp?) - and you need to lower the voltage and amps. serious even if u get it to oscillate your going to be dealing with some serious unwanted hum.

you need either an isolation transformer or just connect two ac step down transformers into each other - just look on the internet. you need to full wave rectify it and then you need a filter network with some big ass resistors and caps.

i've nevr heard of a 220V Neon - i'm not doubting it's existance - but i highly recomend you buy some 'normal' neons - which usually turn on at about 80volts. i'm guessing your '220v' neons just have a big drop down resistor in them.

everything i have mentioned can be bought for under 5$ if you look around right

regardless - after you have a SUITABLE POWER SUPPLY and not a instant death crap job - the circuit should work just fine on 220v - but you are going to have to change all the resistor values - and yes prob the watt size. but i'm not doing the math for you! Smile

all the best - good luck - i LOVE the sound of neons and use them all the time - but please make a real power supply first!! i dont want to be blamed by your girlfriend when you die - or go blind - it's also fairly common that the ghost of edison and tesla will come out of the sparks made by improper use of mains line and make you gay and also captain of the solaris space ship - which might be ok but your girlfriend will sue me

Wink

dave wright
www.notbreathing.com

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

Ok ok I admit the dimmer was a nut-job.. So what your saying is even if I had a transformer from 220V mains to ~ 120V. I would have a crappy hum on my output even after filtering ? What about all the modular synths powered by mains why don't they sound like crap then ?

horchacha · Joined: Sep 05, 2007 Posts: 8 Location: tucson, az

voltage regulation

the filter caps and resistors after your full wave rectifier are for
eliminating hum

a quality power supply is the heart of anything you are going to make

don't give up - just maybe read a bit about power supplies

Lofi Ninja · Joined: Oct 25, 2008 Posts: 143 Location: Jupiter

Yes I should.. Never had any "reason" to before.. When power was on everything was fine..