Search found 23 matches

by marcusriley
Wed Feb 12, 2020 12:05 am
Forum: Music Tech DIY
Topic: small question about high-pass filter
Replies: 6
Views: 661

small question about high-pass filter

Hello All, I have been experimenting with the basic single-order low-pass and high-pass active filters, like the ones below. https://www.electronics-tutorials.ws/wp-content/uploads/2013/08/fil20a.gif?fit=444%2C226 https://www.electronics-tutorials.ws/wp-content/uploads/2013/08/fil91.gif?fit=444%2C25...
by marcusriley
Mon Feb 10, 2020 10:24 pm
Forum: Music Tech DIY
Topic: LM13700 tester circuits?
Replies: 12
Views: 1516

Re: LM13700 tester circuits?

i think some kind of blinking circuit would really help to debug some things, since i know power rails can get pinned.
by marcusriley
Mon Feb 10, 2020 5:43 pm
Forum: Music Tech DIY
Topic: LM13700 tester circuits?
Replies: 12
Views: 1516

Re: LM13700 tester circuits?

Hi - I'm looking for a simple circuit that lets me test the lm13700. That's why I posted in this thread.
Thanks.
by marcusriley
Mon Feb 10, 2020 3:34 pm
Forum: Music Tech DIY
Topic: LM13700 tester circuits?
Replies: 12
Views: 1516

Re: LM13700 tester circuits?

Hi all - Sorry to bring up an old thread. Not sure what the etiquette is on this. I'd like a simple LM13700 circuit to drive an LED. I was experimenting with the single-OTA oscillator in the application notes, but started to burn out all the buffers (I think). With the VCA circuit, it would require ...
by marcusriley
Fri Dec 06, 2019 5:24 pm
Forum: Music Tech DIY
Topic: voltage regulators
Replies: 8
Views: 782

voltage regulators

Hi - I had a dumb questions about voltage regulators, since I'm having a little trouble making sense of the datasheet and haven't worked with them much before. I'm using a a version of the "battery charger" example in the LM317 datasheet (http://www.ti.com/lit/ds/slvs044x/slvs044x.pdf) - the only di...
by marcusriley
Fri Dec 06, 2019 12:28 am
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Yes, the only downside is that there is ultimately a trade-off between the maximum and minimum brightness, which I suppose is to be expected. I think better behavior over a smaller range is preferable to the normal slog. Since the design I'm working on already has 8 LDRs, I'm hesitant to try your li...
by marcusriley
Thu Dec 05, 2019 11:40 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Yes, I really rather like this driver - I'm still experimenting to get a more full "off" of the LED (maybe a diode in series?), since it glows, just barely, at the most negative excursion - but it is serving me pretty well, so thank you!
by marcusriley
Wed Dec 04, 2019 12:51 am
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Just tried the "Mutant Vactrol" method and found that it works quite well. The only thing worth pointing out is that it doesn't quite turn off all the way and it doesn't quite fully saturate. I'm assuming this is the "S Curve" in action, but I wanted to ask if you thought adding a negative bias at t...
by marcusriley
Tue Dec 03, 2019 11:41 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Slope still a little too steep? I still suggest the dual-vactrol-feedback configuration. :hihi: It's not bad - I was just a bit confused because devinw1 said that circuit was an "on off driver. " I'm sure the double-vactrol method will work the best, but it seems like something that should be reser...
by marcusriley
Tue Dec 03, 2019 10:18 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

It looks to me that the transistor part of this circuit is more or less the same one I used at first (without the op-amp buffer, though). So, I'm confused about what makes that one a "switch" and this one not?
by marcusriley
Tue Dec 03, 2019 7:46 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

I went back and re-read your original post. I didn't realize we were talking about optocouplers. It generally takes some tweaking to get everything right with a vactrol. I think he's making his own, but your circuit offers a lot of trimming options. I am trying to work with some homemade vactrols, ...
by marcusriley
Tue Dec 03, 2019 5:50 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Hey there- Just tested the Op Amp "Bicolor LED" circuit - noticed a few things: 1. The LED never turns completely off. I can experiment a bit more with the input resistor and the LED used. In some ways, this doesn't matter.. except for: 2. There is still a major jump in the LDR response from darknes...
by marcusriley
Tue Dec 03, 2019 5:09 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Thanks for the suggestion, J3RK - it would be a relief to get this into a single op-amp. Putting in the feedback loop compensates for the bias, right? Found this in the Muffwiggler archive, which uses a bias trimmer - is this a hard switch also? https://www.muffwiggler.com/forum/userpix2/53883_singl...
by marcusriley
Tue Dec 03, 2019 3:49 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

The original schematic you posted is just an on off driver. My understanding was that it was a buffer feeding a transistor amplifier - and that transistors naturally produce an exponential response. it definitely doesn't simply produce a hard "off"/"on" - there is some amount of expression througho...
by marcusriley
Tue Dec 03, 2019 12:57 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Just beginning to dig in, but reading through the Schmitz article, it seems that my driver is already exponential - it's just not compensated. Is the variation in thermal drift really significant enough to merit all of the additional circuitry, when it comes to simply driving an LED? I know that the...
by marcusriley
Tue Dec 03, 2019 12:42 am
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Orgia Mode wrote: what is your input? e.g. 0-10v or something else?
Yes, that's right. Thanks for the links to the Open Music Labs article.. might as well start the 100 readings sooner rather than later!
by marcusriley
Mon Dec 02, 2019 10:54 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

The problem is that this type of conversion requires thermal compensation to maintain that linearity across different ambient temperatures as well as across the full range of inputs. Then you have the issue of dialing in the trimmers to make it work with your LDR which is probably has 10-20% error....
by marcusriley
Mon Dec 02, 2019 7:30 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

That looks like a fantastic solution - I will definitely try it out for a future project. For my current issue, though, it would be helpful to look at some possibilities that use a single pairing, if there are other ideas.
by marcusriley
Mon Dec 02, 2019 7:04 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Orgia Mode wrote:So are you using the LED and LDR in a vactrol configuration?
Yes.

Are you saying there are a lot of other problems with the schematic you attached or the one that I attached?
by marcusriley
Mon Dec 02, 2019 6:29 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

Oops, sorry about that.

Picture file
by marcusriley
Mon Dec 02, 2019 5:40 pm
Forum: Music Tech DIY
Topic: LED Driving
Replies: 41
Views: 2957

LED Driving

Hi everyone, I know there is *a lot* of information on how to drive LEDs on this forum, so I'm sorry to post anew. I'm just hoping someone can talk me through building a slightly more sensitive design - sometimes I get lost in the more technical discussion. I've been using the attached design. It wo...
by marcusriley
Mon Oct 21, 2019 11:49 pm
Forum: Music Tech DIY
Topic: Voltage-Controlled Resistors (FET and Otherwise)
Replies: 10
Views: 668

Voltage-Controlled Resistors (FET and Otherwise)

Hi - I'm new to electronics and I'd like to have some voltage-controllable elements in my circuit. It seems like the most direct way to do this is to make something that functions like a variable resistor. I've seen some examples of FET Voltage-Controlled Resistors (VCRs) - but they generally seem t...
by marcusriley
Mon Oct 21, 2019 11:43 pm
Forum: Artist Discussion
Topic: Roland Kayn
Replies: 53
Views: 12273

http://telesoniek-atelier.nl/

I believe some of these articles reveal some of what he was working with..

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