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...

i think some kind of blinking circuit would really help to debug some things, since i know power rails can get pinned.

Hi - I'm looking for a simple circuit that lets me test the lm13700. That's why I posted in this thread.
Thanks.

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 ...

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...

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...

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!

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...

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...

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?

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, ...

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...

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...

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...

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...

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!

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....

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.

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?

Oops, sorry about that.

Picture file

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...

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...

http://telesoniek-atelier.nl/

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