In need of a specific sound-to-light module

[BrownOut]

A belatedly Happy birthday to you too, fellow Pisces.
I'm now 46, not far behind you.

Some info about guitar pickups you mind find of interest:

726-750 - Seymour Duncan/Basslines
(paragraphs #742 and #743)

Guitar Pickups Simulation


**broken link removed**

I think we're going to end up adding a high input impedance buffer by the time we're through.

 

[ddlooping]

It's not really parallel. The ground is wired directly to the lower connection shown on the schematic, and the signal is wired to the top one.

Sorry if I'm being stupid but...
The signal still has to come out of the guitar for it to be heard, so it would have to be connected both to the circuit and the guitar output socket.
The "-" on guitar pickups and outputs is also always grounded.
As I don't see any "sound" output on the circuit, wouldn't that created a parallel connection?

 

[ddlooping]

I think we're going to end up adding a high input impedance buffer by the time we're through.

Sorry for having pulled you into this, I hope you're not starting to regret it. **broken link removed**

 

[BrownOut]

Not at all. I have been intrigued by your project from the start. I really don't think you're going to be very happy with the performance of the simple circuit, and you'll eventually want something better, however.

 

[audioguru]

I think your guitar players will be upset when they must play in the dark for the LEDs to be seen.
I have some fading multi-colour LEDs in my computer room now in daylight. They are visible but are not bright. In the dark they are blindingly bright.
LEDs shine only in a single direction. To a side they are barely visible.

Hi BrownOut,
Your second opamp might be destroyed by the AC signal (its negaive voltage) at its input since it does not have a negative supply voltage.
If your second opamp is inverting then it won't have this problem. I guess an LM358 single-supply dual opamp could be used.

 

[BrownOut]

Hi BrownOut,
Your second opamp might be destroyed by the AC signal (its negaive voltage) at its input since it does not have a negative supply voltage.
If your second opamp is inverting then it won't have this problem. I guess an LM358 single-supply dual opamp could be used.

Good point. This was supposedly a working circuit which I added a couple components. We can modify the amp for inverting operation.

 

[ddlooping]

Not at all. I have been intrigued by your project from the start.

Good, I'm glad to hear it.

I really don't think you're going to be very happy with the performance of the simple circuit, and you'll eventually want something better, however.

Well, we can only but try. Having that widget in the perspex version of the guitar would be great but it's not essential.
If I do end-up wanting/needing something better I'll look more deeply into it when I have more means and time.

I think your guitar players will be upset when they must play in the dark for the LEDs to be seen.
I have some fading multi-colour LEDs in my computer room now in daylight. They are visible but are not bright. In the dark they are blindingly bright.
LEDs shine only in a single direction. To a side they are barely visible...

Hello audioguru, and thanks for joining us.

I understand your concern but I'll make sure to show visitors to the site both the effect of the LEDs in a light and dark environment.
The effect in the former might not be striking but it will hopefully still be visible and add an ethereal touch to the perspex Ghost.
I'm also hoping the perspex will spread/diffuse the light generated by the LEDs.

 

[BrownOut]

Now that I think about it, there are a couple problems with the circuit I drew. The fader circuit won't work like we want it to. I'll post a revised drawing soon.

 

[ddlooping]

Now that I think about it, there are a couple problems with the circuit I drew. The fader circuit won't work like we want it to. I'll post a revised drawing soon.

Thanks once again, BrownOut.

No hurry though, the festival is not before the 8-9th of May.

I'll wait for the circuit to be finalised before I go and get the components.

 

[BrownOut]

Here is rev2. I made some changes for the pickup's hight output impedance. V2 and R7 are NOT part of the circuit, but intended to model the pickup for simulaion. The diodes between the two opamp's are intended to protect the 2nd amp from damaging voltage. They may not be needed if use use an LM358, but when I looked at the Fairchild datasheet, it said min input is 0V, so I suggest to just leave them in. ( others will disagree, I"m sure ) Any diodes that will switch at audio frequencies will do for D3 & D4. Switch 1 and 2 can be a 3-way switch, as long as the swtich has 3 seperate pairs of contacts, and is not a 3-to-1. Otherwise, switch 2 can be a spdt. Make sure you use good, medium performance op-amps. A 741 probably won't cut the mustard.

 

[ddlooping]

Thanks again BrownOut.

I'll try and get the components asap. (too late to get them today I'm affraid)

 

[BrownOut]

Change R12 to a 1k variable resistor. I'm still fooling with this. I'm updating the schematic to reflect this change.

PS: You won't get full range from the fader. Might need to reduce R11 slightly. I done fooling with this.

 

[ddlooping]

Change R12 to a 1k variable resistor. I'm still fooling with this. I'm updating the schematic to reflect this change.

PS: You won't get full range from the fader. Might need to reduce R11 slightly. I done fooling with this.

Ok, I'll let keep you updated. **broken link removed**

 

[BrownOut]

R1 should be 100 ohms, as in the original Musicator. Changing the value will change the brightness.

 

[ddlooping]

R1 should be 100 ohms, as in the original Musicator. Changing the value will change the brightness.

I take it it's the maximum brightness when the LEDs are always on and the peak brightness when it changes dynamically.

I thought you were done with this?
(not that I mind you're not)

 

[audioguru]

Hi BrownOut,
On your new schematic:
1) The first opamp is inverting with a 15k input impedance so it throws away half the input signal level. If it is non-inverting then it can have a high input impedance for a small signal loss.
2) The diodes will not be needed if the second opamp is an inverter since then its inputs will never go negative if its gain is 1.

 

[BrownOut]

AG makes some good points. But I'd say let's just leave it as it is for now.

 

[ddlooping]

AG makes some good points. But I'd say let's just leave it as it is for now.

Ok, thanks BrownOut.

I've asked a friend who used to work in Formula 1 racing (not sure what his exact job was but it had to do with electronics) to look into it.
Not only did he agree but apparently he's got a friend and ex-colleague who's quite a wizard in the field and might be willing to help too.