debugging a lamp driver

[lightningfingers]

ok i spent most of yesterday and all of this morning making a new lfo with a completely new set of parts. every component is checked and working and still there is no oscillation.
i tried most of the things we discussed in the previous posts and nothing worked.
which leads me to this; about the only thing we havent discussed is the transistor(s)
could there be any problems related to them?

[gez]

which leads me to this; about the only thing we havent discussed is the transistor(s)
could there be any problems related to them?

If the Darlington is connected up ok then there's not a lot that could be wrong, they're not static sensitive or anything.  

I don't really understand why two trimpots have been used, it seems a little odd.  Does he give some advice on how to set these and if so could you link to it?  What sort of resistance do you have on these trimpots?  If the lower one is set to bugger all then there's the danger of loading/grounding the LFO's signal.

Are you still getting 'unstable' readings from the LFOs output?  If so then it's probably working ok.

[lightningfingers]

its here
on the easyvibe page.
im still getting the unstable readings, yeah, but the light still wont work.

[gez]

but the light still wont work.

When you turn the trimpot(s) does the light change, i.e. can you make it go from off to on, or is it permantly off/on? (nothing to do with the LFO here, just want to find out if the Darlington is working ok).

[lightningfingers]

yeah adjusting the trimmers will make the light go off, on and everywhere inbetween.
i put a new darlington pair in there when i replaced the board so it should be ok.

definately having some fun with this one :wink:

[gez]

yeah adjusting the trimmers will make the light go off, on and everywhere inbetween.
i put a new darlington pair in there when i replaced the board so it should be ok.

definately having some fun with this one :wink:

Don't know what else to suggest other than do you know someone with a scope?

[lightningfingers]

Don't know what else to suggest other than do you know someone with a scope?

no i tried my school but they wont let me use thiers

do you know of another LFO that might work in this circuit?[/quote]

[gez]

do you know of another LFO that might work in this circuit?

PM me with your email address and I can sort you out with something if you like.

[lightningfingers]

just click that link down there that says "email" :wink:

[gez]

Can't send attachments via the forum which is why I asked for your address...

I drew this up a few weeks ago and posted it here.  Not exactly what I had in mind but It'll probably do



Use a BS170 for the MOSFET supplying the 4049UB.  Adjust the wiper of its trim down from 5V til you measure 3V at the source.  In theory it's possible to get ones with large thresholds (in which case you'd get voltages under 3V and wouldn't be able to get higher), but I've never come across any - all have worked in this type of circuit so far.

Stick your lamp from V+ to the drain of the other MOSFET (the one connected up to the depth pot).  I don’t know what the current draw of the bulb you intend to use is, but you’ll probably have to use a power MOSFET there.  Adjust the wiper up from ground til you get an even range across the Depth pot.

ESR have all the parts

www.esr.co.uk

It's a triangle wave.  If you wanted a sine, I suppose you could use something along the lines of the EA trem's LFO and hook it up to the MOSFET driver shown above (plumb the LFO output in via the 4u7 cap).  The trim for adjusting the MOSFET could be slung across the rails, or you could keep the regulator.

[lightningfingers]

okay, ill get some parts tomorrow and let you know how it goes.

and thanks for this it is greatly appreciated

[gez]

Forgot to add, ground the inputs of the unused inverters of the 4049UB.

[lightningfingers]

okay its done and the bulb oscillates, but how fast is it supposed to go? it seems to get too fast at the high end, and the bulb loses its oscillation

[gez]

okay its done and the bulb oscillates, but how fast is it supposed to go? it seems to get too fast at the high end, and the bulb loses its oscillation

Well what do you expect if you use bulbs instead of LEDs!    

Top speed is around 12Hz.  All you have to do to slow it down is increase the 130k resistor (don't worry it won't affect amplitude or anything).  Try a 160k (just under 10Hz) and if that’s still too fast then 180k (just under 9Hz).  If you want the lower range to go slower then decrease the value of the 1k stop-resistor attached to the 10k pot (this may upset the linear ‘feel’ to the pot though - depends how slow you take it).

PS if anyone's wondering why the ciruit runs at 3V it's to reduce current consumption and to reduce current spikes.  The spikes are so miniscule at this voltage you get tick-free operation (though this isn't guaranteed, it's still advisable to obey the rules of good layout!).  Current draw is usually under .5mA for the LFO alone (if you use the regulator stated - it's micropower).  Adjustable regulator could be used to get the 3V but it would add a few milliamps onto the bill.

[Electron]

im building the modded easyvibe by pedro freitas, (gotta love that guy and his lunchboxes)
and i built the LFO part first, and it is not working. :evil:
the battery voltage is 8.64 volts and the lamp works.
how do you debug one of these?
im guessing you cant use an audio probe.

Hi LightningFingers,

I assume you use the layout that is available on the net.

Make sure, there is no short on the PCB. I spent a couple of hours to figure out why my EasyVibe would not LFO only to find that there was a small connection from the LFO LEDS to ground. I scraped away the wrong connection (possibly due to a not so good toner transfer) and voila.

Kind Regards,

Electron

[gez]

Make sure, there is no short on the PCB. I spent a couple of hours to figure out why my EasyVibe would not LFO only to find that there was a small connection from the LFO LEDS to ground. I scraped away the wrong connection (possibly due to a not so good toner transfer) and voila

Now you tell us!!!

[lightningfingers]

Make sure, there is no short on the PCB

well i perfed it so that wouldnt be an issue

and also the one gez drew up works well :mrgreen:

[Electron]

:shock:    :shock:  :oops:

Seems like my response from 9.03 am was somehow lost in interspace.

Anyhow, I did not mean to rain on anyone's parade, especially not GEZ´s.

With my Easyvibe it was my fault, since, as said, the toner transfer did not come out very nice.

Glad you were able to fix it LightningFingers!

Do you plan to do the Feedback mod?

I wish my EasyVibe had a bit more warmth.

Cheers!

Electron
:wink:

[lightningfingers]

actually the feedback mod adds a lot of *interesting* tones. try it you havnt already