Yup, adjust both slopes, and adjust the delay of the second led's slope kicking in

Ok, let me give it some thought, and I'll get back to you

 

OK, thanks! I just finished drawing the breadboard layout of the theremin on VeeCAD, using a light dependant resistor to replace the 2 transistors, don't think it'll have the same effect, but then at least I have the theremin ready for when we get the rest of the circuitry, but I don't think I'll be building it tonight -- else it's gonna turn 01h00 and I'm still not in bed ;-) one or two more "Borkum Riff Bourbon Whiskey" pipes and I'm off.

Thank cmartinez, until tomorrow

 

Ok, here's my idea: what we need to make is a voltage ramp generator circuit of the ramp-up-and-hold type.
After that, we build another circuit and trigger it in tandem with the previous one using a 555 timer.
But first, we build the simplest one and test it.

Here are a few links that I'm planning to study later... see which circuit is more practical for our purpose:

http://www.hqew.net/events/news-article/9665.html
http://www.seekic.com/circuit_diagr...generator_circuit_composed_of_the_TA7507.html
http://www.daenotes.com/electronics/digital-electronics/ramp-generators-types-methods
https://www.circuitlab.com/circuit/xw65e2/voltage-ramp/
http://smallmr.com/wordpress/small-display-layout-with-variable-led-lighting/
http://homepages.which.net/~paul.hills/Circuits/RxDecoder/RxDecoder.html

 

Here's an idea.

 

Here's an idea.

Excellent, I'll sim it in LTspice and post it later.

 

Analog design kind of resembles DOS in today's world. Very few people can do it well, and it almost looks like magic compared to an MPU.

 

Analog design kind of resembles DOS in today's world. Very few people can do it well, and it almost looks like magic compared to an MPU.

I guess that makes me an oxymoron.... I'm an expert in DOS but I suck at analog design...

 

There you go, here's the LTspice model, and an image of the circuit with values and all... the voltage ramp up is not exactly linear, but it should get the job done...

 

That ramp should be deadly straight. The only reason it curves is that you ran out of Vcc.

http://forum.allaboutcircuits.com/blog/low-temperature-drift-jfet-constant-current-circuit.579/

 

You got 0.7 seconds of straight line. Most musical notes don't last that long and the capacitor can be changed and the Vcc can be changed.

 

You got 0.7 seconds of straight line. Most musical notes don't last that long and the capacitor can be changed and the Vcc can be changed.

Yeap, usually notes don't last that long, that's why I added the pot to the circuit... I still don't get how to "straighten" that line, though... would I need to use a higher voltage?

 

Just studied your blog... very interesting... I'm learning something, thanks...

 

That ramp should be deadly straight. The only reason it curves is that you ran out of Vcc.

I still don't get how to "straighten" that line, though... would I need to use a higher voltage?

I thought I said that.

 

Just studied your blog... very interesting... I'm learning something, thanks...

Thanks for mentioning it. There is a lack of feedback about blogs and I often think nobody notices them or gets any education from them.

 

I thought I said that.

Yeah you did... but I did increase the battery's voltage to 12V and it still worked the same...
I got lots and lots to learn regarding analog stuff...

 

It's always going to curve in the last 2 volts because the transistor is running out of voltage. The trick is to design the machine to only need the ramp to operate in the bottom part of the voltage. Maybe use a 12 volt supply for the op-amps and use a zener to clip the ramp at 9 volts...

 

Ok hi #12! I'm back but only for 2h, have to get to bed at 21h00 to get up early enough for early gym tomorrow.

Ok Flat top Ramp and Dump, explain please. What part of the circuit is this? Does it replace PWM or (I guess) is the input to PWM's brightness, so I can adjust the angel of the slope of the led turning on?

 

possible limitations:
I have 2x 12V 2A switch mode power supplies
5x 12V 2.5A switch mode power supplies
10x 2A USB chargers
...
does it have to be 2N4416, I have:
2N3904
2N2222
can't get 2N4416 from my usual supplier (www.mantech.co.za), www.communica.co.za has it, but I have to courier the parts which makes it insanely expensive
I'm browsing "field effect transistor" at http://www.mantech.co.za/Stock.aspx?Query=field effect transistorand seems like there's many to choose from, @#12 could you maybe throw an expert eye over the selection of field effect transistors mantech has got, to get me one that'll work. thanks very much for your work so far.

Or give me parameters and I'll figure it out; or try to

edit:
maybe 2N7000BU
edit:
or
Part Number BS107 TAPE
Description FET N-C TO92 200V 0A15

 

What? Dimming LEDs? I thought we were working on a piano keyboard.
The ramp circuit is a response to what Martinez was searching for...ramps. See? It even has a piano key on the left side.

Anyway, a ramp is part of a pwm, and a ramp can end in a down ramp or a sudden stop. This being a piano, I expected a sudden stop unless one of the pedals is depressed.

 

@#12 watch the video at the end of the link in the first post, then you'll know the whole story. I need to mimic what he does with phototransistors with optocouplers, a 0.1uf Ceramic cost R0.33 a visible light spectrum phototransistor cost R150 each, so that's not an option, I don't have that much money