Univibe Rate LED.. can't figure it out.

Started by no one ever, January 06, 2006, 05:02:06 PM

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no one ever

Yep, I searched. Just came up with this, which simply alludes to the solution being easy and simple.

I was pondering, today, how I could make this clone different from any other clone. I came up with a few ideas that, with my limited skills and knowledge of mathematical formulas (recently learned formulas for capacitors and resistors in series/parallel, aren't you proud), could implement, such as footswitchable chorus/vibrato mode, a big ol' rate knob, and maybe fudge around with the phase shift caps. However, there was one notion that has been fascinating me for days, and that is the possibility of an LFO rate LED.

Anyone willing to walk me through the process of adding on a 3.5v rated LED to a >17v power line feeding a 12v lamp?
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no one ever

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no one ever

#2
http://led.linear1.org/1led.wiz ... using radioshack's 'typical voltage' for forward voltage and assuming an 18v power supply, i should simply put an 820r 1W resistor. which is odd, because there are no >.25W resistors in the entire vibe circuit.

EDIT: realized that LED can have its own supply, as it seems that the LFO is modulating how much ground the lamp is connected to. However, even assuming a 9v supply, the ohmage came out to only 350r!

and assuming 15v supply (a bit much to have a 9v JUST for the LED) off the regulator, i'd need a .26W resistor. ugh.
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no one ever

feel like i'm beating a dead horse... last bump.  ???
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newperson

hi,

did you get your neovibe working?  how does it sound?  how does the phase sound?
-paul.

no one ever

Quote from: newperson on January 07, 2006, 05:12:53 AM
hi,

did you get your neovibe working?  how does it sound?  how does the phase sound?
-paul.

:icon_redface: it's yet to be etched (smallbear order isn't here yet w/ speed pot+ box and other niceties)
(chk chk chk)

R.G.

I should share with everyone what I told no one ever.

The simple way to do this is to put an LED and a large value resistor in parallel with the light bulb. The resistor needs to be large to drop the large voltage that the light bulb works on and to limit the LED current. You want to use an ultrabright or super bright LED and a resistor that keeps the added current on the lamp driver down in the 1-2ma range.

The lamp driver is a weak point of the Univibe design. A TO-92 plastic transistor can ...barely... do it. That's one reason I put pads on the Neovibe layout for a TO-220 transistor to do that job. Everyone seems to get away with the TO-92 mostly, but I have repaired a number of real univibes that have this transistor fried. So keep the added current on this one down with a very bright LED that's visible with low currents.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

spudulike

Check out JC Maillet's site for mucho Univibe cloning info.

http://www.lynx.bc.ca/~jc/pedalsUnivibe.html

Lots of good info on the bulb driver cct including some useful offset controls and a rate LED.

LyleCaldwell

#8
Quote from: R.G. on January 08, 2006, 10:40:09 AM
I should share with everyone what I told no one ever.

The simple way to do this is to put an LED and a large value resistor in parallel with the light bulb. The resistor needs to be large to drop the large voltage that the light bulb works on and to limit the LED current. You want to use an ultrabright or super bright LED and a resistor that keeps the added current on the lamp driver down in the 1-2ma range.

The lamp driver is a weak point of the Univibe design. A TO-92 plastic transistor can ...barely... do it. That's one reason I put pads on the Neovibe layout for a TO-220 transistor to do that job. Everyone seems to get away with the TO-92 mostly, but I have repaired a number of real univibes that have this transistor fried. So keep the added current on this one down with a very bright LED that's visible with low currents.

OK, got it - positive from the transistor directly to ground, not using the side of the lamp circuit that connects to the regulator. 
What does this button do?

psionicaudio.com

RedHouse

Quote from: R.G. on January 08, 2006, 10:40:09 AM
I should share with everyone what I told no one ever.

The simple way to do this is to put an LED and a large value resistor in parallel with the light bulb. The resistor needs to be large to drop the large voltage that the light bulb works on and to limit the LED current. You want to use an ultrabright or super bright LED and a resistor that keeps the added current on the lamp driver down in the 1-2ma range.

The lamp driver is a weak point of the Univibe design. A TO-92 plastic transistor can ...barely... do it. That's one reason I put pads on the Neovibe layout for a TO-220 transistor to do that job. Everyone seems to get away with the TO-92 mostly, but I have repaired a number of real univibes that have this transistor fried. So keep the added current on this one down with a very bright LED that's visible with low currents.

BTW what TO-220 transistor is the sub?

LyleCaldwell

Mouser part number 511-L7815ACV which is a positive 15 volt regulator (7815).  $0.40 each.
What does this button do?

psionicaudio.com

R.G.

I'm not being clear again.

Take a resistor from the hot side of the lamp to the anode of an LED. Take the cathode of the LED to the collector of the driver transistor. The LED needs to be an ultrabright type. The resistor should limit LED current to no more than one ma or so, so it'll be in the 18K to 33K range. That way, the LED shows a brightness that varies with the lamp. It may not go fully on or off. There are other ways, but this is simplest.

As to TO-220's, I'd try
BD134/BD137/BD139, MJE180/MJE181; you could also try darlingtons - TIP110/TIP120, JFE270, MJE800. Basically, you want to get anything in a package that's bigger than the TO-92. Even the longer version of the TO-92 is good for one watt.

R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

LyleCaldwell

Quote from: R.G. on January 30, 2006, 04:21:13 PM
I'm not being clear again.

Take a resistor from the hot side of the lamp to the anode of an LED. Take the cathode of the LED to the collector of the driver transistor. The LED needs to be an ultrabright type. The resistor should limit LED current to no more than one ma or so, so it'll be in the 18K to 33K range. That way, the LED shows a brightness that varies with the lamp. It may not go fully on or off. There are other ways, but this is simplest.

As to TO-220's, I'd try
BD134/BD137/BD139, MJE180/MJE181; you could also try darlingtons - TIP110/TIP120, JFE270, MJE800. Basically, you want to get anything in a package that's bigger than the TO-92. Even the longer version of the TO-92 is good for one watt.



Hmm, I did it "wrong" but it works.  I have the resistor connected to C of the unmarked transistor (should be Q13) just above C23 (all referring to the GGG PCB) and then to the anode, with the cathode connected to ground (I used the otherwise empty Pad D next to the power connections).

It pulses in time (though alternating with the lamp rather than at the same time) and since I used a pot rather than a fixed resistor it lets me fine-tune the depth and mix a bit.

Any reason this might blow up on me?
What does this button do?

psionicaudio.com

no one ever

Quote from: spudulike on January 08, 2006, 11:49:38 AM
Check out JC Maillet's site for mucho Univibe cloning info.

http://www.lynx.bc.ca/~jc/pedalsUnivibe.html

Lots of good info on the bulb driver cct including some useful offset controls and a rate LED.

JUST read that... the first time around, I couldn't find that article on the page.


is the parallel trim really only 500 ohms? And I don't quite understand how a parallel resistance can restrict a LED's supply voltage... Shorting the voltage to ground?
(chk chk chk)