# Electrovibe Rate LED



## JPierpont-Finch (Sep 2, 2021)

I had this idea today and before I did a dive into the circuit I was curious if anyone else had looked into or added an LED that flashed along with the LFO rate in the Electrovibe.


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## Big Monk (Sep 2, 2021)

JPierpont-Finch said:


> I had this idea today and before I did a dive into the circuit I was curious if anyone else had looked into or added an LED that flashed along with the LFO rate in the Electrovibe.



I’ve been thinking about it as well. My Carl Martin Surf Trem has a speed LED as well as my EHX Good Vibes. 

I don’t know enough about the circuits to know how they are implementing it.


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## danfrank (Sep 2, 2021)

It's kind of hard with this project because the build docs aren't available yet. There is another PCB company (Madbean) that has a similar project and attached here is a pic of the LFO of the univibe. I'm sure both circuits are similar so you can add an LED and 10k (R54 in pic) resistor to the circuit where it's shown in the attached pic.
Hope this helps...


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## JPierpont-Finch (Sep 3, 2021)

That is actually super helpful.  Now it is just a matter of figuring out which one is Q11.


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## Big Monk (Sep 3, 2021)

JPierpont-Finch said:


> That is actually super helpful.  Now it is just a matter of figuring out which one is Q11.



If I am reading the Electrovibe schematic correctly and matching the corresponding transistor in the Madbean schematic, Madbean's Q11 corresponds to Pedal PCB's Q1/Q2.

So, you'd insert the rate LED and corresponding resistor to LFO Out on the Analog LFO block on the schematic. Seems like the middle lug of the Speed 1.1/1.2 pad is the logical place and then run a wire to ground with the resistor. You may want to tie it to the Effect bypass switch so that when you switch it off, you also switch off the Rate LED.

Interesting stuff. I was going to forego this as I thought it would be more difficult but it seams I'll have to factor this in to my build.


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## Robert (Sep 3, 2021)

You might want to test it before drilling a hole for the LED...   

The amplitude of the LFO increases as the Rate control is turned up.    At slower rates the LED won't be very bright.


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## Big Monk (Sep 3, 2021)

Robert said:


> You might want to test it before drilling a hole for the LED...
> 
> The amplitude of the LFO increases as the Rate control is turned up.    At slower rates the LED won't be very bright.



This was something I had thought about. I only have experience with Rate LEDs on my Carl Martin Surf Trem and my EHX Good Vibes. Both of those pedal's LEDs stay nice and bright even at slow speeds but I have no idea what circuitry they are using to achieve that.


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## JPierpont-Finch (Sep 3, 2021)

I'll definitely be testing it out.  I am planning on using the rate LED with a UV LED to activate a glow in the dark screenprint on the case so the low brightness may not be a dealbreaker.


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## JPierpont-Finch (Sep 3, 2021)

Big Monk said:


> If I am reading the Electrovibe schematic correctly and matching the corresponding transistor in the Madbean schematic, Madbean's Q11 corresponds to Pedal PCB's Q1/Q2.
> 
> So, you'd insert the rate LED and corresponding resistor to LFO Out on the Analog LFO block on the schematic. Seems like the middle lug of the Speed 1.1/1.2 pad is the logical place and then run a wire to ground with the resistor. You may want to tie it to the Effect bypass switch so that when you switch it off, you also switch off the Rate LED.
> 
> Interesting stuff. I was going to forego this as I thought it would be more difficult but it seams I'll have to factor this in to my build.


Would you do just one LED to both speed pots or do an LED for each?  Only one should be active at a time, right?


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## Big Monk (Sep 3, 2021)

JPierpont-Finch said:


> Would you do just one LED to both speed pots or do an LED for each?  Only one should be active at a time, right?



I imagine only one LED is required.


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## Bricksnbeatles (Sep 8, 2021)

It would require some perf/stripboard work, but I don’t see any reason why you couldn’t just use an additional LDR positioned near the bulb to modulate the brightness of an LED . You could put a series resistor as the CLR to set maximum brightness and a trimpot in parallel with the LDR to lower the maximum resistance (and therefore raise the minimum brightness) and alter the resistance curve.


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