Forums

Simple circuit to flash an LED from RF

Started by amdx July 31, 2022
I'd like to setup a high Q LC to receive a local Radio station probably 
charging a cap, when the charge is high enough flash an LED.
Maybe set the trigger point of an SCR, or could just a zener do it. I 
don't have LT spice, so please don't post and answer with that.

                                 Thanks, Mikek

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On Sun, 31 Jul 2022 10:56:27 -0500, amdx <amdx@knology.net> wrote:

>I'd like to setup a high Q LC to receive a local Radio station probably >charging a cap, when the charge is high enough flash an LED. >Maybe set the trigger point of an SCR, or could just a zener do it. I >don't have LT spice, so please don't post and answer with that. > > &#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080; Thanks, Mikek
I expect that a strong radio station could light an LED visibly continuously, given a good well-matched antenna. Or charge a cap and use a discharge circuit to get bright blinks. Here's my high-voltage low current blinker: https://www.dropbox.com/sh/yaqbi52vbpo6uyc/AABPAczwj1zv26-fwI4LvJyha?dl=0 But LT Spice is free, easy to learn, and a wonderful tool for stuff like this.
31.07.22 22:58, jlarkin@highlandsniptechnology.com wrote:
>On Sun, 31 Jul 2022 10:56:27 -0500, amdx <amdx@knology.net> wrote: > >>I'd like to setup a high Q LC to receive a local Radio station probably >>charging a cap, when the charge is high enough flash an LED. >>Maybe set the trigger point of an SCR, or could just a zener do it. I >>don't have LT spice, so please don't post and answer with that. >> >> &#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080; Thanks, Mikek > >I expect that a strong radio station could light an LED visibly >continuously, given a good well-matched antenna. Or charge a cap and >use a discharge circuit to get bright blinks. > >Here's my high-voltage low current blinker: > >https://www.dropbox.com/sh/yaqbi52vbpo6uyc/AABPAczwj1zv26-fwI4LvJyha?dl=0 > >But LT Spice is free, easy to learn, and a wonderful tool for stuff >like this. >
Tuned LC with diode to big low leakage cap Then a BJT multivibrator, can operate in nA Assign very low duty cycle for LED -- Klaus
On Mon, 01 Aug 2022 03:13:19 +0300, Klaus Kragelund
<klauskvik@hotmail.com> wrote:

>31.07.22 22:58, jlarkin@highlandsniptechnology.com wrote: >>On Sun, 31 Jul 2022 10:56:27 -0500, amdx <amdx@knology.net> wrote: >> >>>I'd like to setup a high Q LC to receive a local Radio station probably >>>charging a cap, when the charge is high enough flash an LED. >>>Maybe set the trigger point of an SCR, or could just a zener do it. I >>>don't have LT spice, so please don't post and answer with that. >>> >>> Thanks, Mikek >> >>I expect that a strong radio station could light an LED visibly >>continuously, given a good well-matched antenna. Or charge a cap and >>use a discharge circuit to get bright blinks. >> >>Here's my high-voltage low current blinker: >> >>https://www.dropbox.com/sh/yaqbi52vbpo6uyc/AABPAczwj1zv26-fwI4LvJyha?dl=0 >> >>But LT Spice is free, easy to learn, and a wonderful tool for stuff >>like this. >> > >Tuned LC with diode to big low leakage cap > >Then a BJT multivibrator, can operate in nA >Assign very low duty cycle for LED
Yes, I was thinking an L-C circuit to boost the voltage at least. LTspice can be downloaded for free from www.analog.com I suggest you get it. boB
On 7/31/2022 2:58 PM, jlarkin@highlandsniptechnology.com wrote:
> On Sun, 31 Jul 2022 10:56:27 -0500, amdx <amdx@knology.net> wrote: > >> I'd like to setup a high Q LC to receive a local Radio station probably >> charging a cap, when the charge is high enough flash an LED. >> Maybe set the trigger point of an SCR, or could just a zener do it. I >> don't have LT spice, so please don't post and answer with that. >> >> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Thanks, Mikek > I expect that a strong radio station could light an LED visibly > continuously, given a good well-matched antenna. Or charge a cap and > use a discharge circuit to get bright blinks. > > Here's my high-voltage low current blinker: > > https://www.dropbox.com/sh/yaqbi52vbpo6uyc/AABPAczwj1zv26-fwI4LvJyha?dl=0 > > But LT Spice is free, easy to learn, and a wonderful tool for stuff > like this. >
I was hoping to do it with just a coil and cap. I have some 6" coils with Q over 1000. Very high impedance a resonance, so might need a lower impedance pickup coil. Their Litz wire, so I don't want to tap them. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
On 7/31/2022 7:35 PM, boB wrote:
> On Mon, 01 Aug 2022 03:13:19 +0300, Klaus Kragelund > <klauskvik@hotmail.com> wrote: > >> 31.07.22 22:58, jlarkin@highlandsniptechnology.com wrote: >>> On Sun, 31 Jul 2022 10:56:27 -0500, amdx <amdx@knology.net> wrote: >>> >>>> I'd like to setup a high Q LC to receive a local Radio station probably >>>> charging a cap, when the charge is high enough flash an LED. >>>> Maybe set the trigger point of an SCR, or could just a zener do it. I >>>> don't have LT spice, so please don't post and answer with that. >>>> >>>> Thanks, Mikek >>> I expect that a strong radio station could light an LED visibly >>> continuously, given a good well-matched antenna. Or charge a cap and >>> use a discharge circuit to get bright blinks. >>> >>> Here's my high-voltage low current blinker: >>> >>> https://www.dropbox.com/sh/yaqbi52vbpo6uyc/AABPAczwj1zv26-fwI4LvJyha?dl=0 >>> >>> But LT Spice is free, easy to learn, and a wonderful tool for stuff >>> like this. >>> >> Tuned LC with diode to big low leakage cap >> >> Then a BJT multivibrator, can operate in nA >> Assign very low duty cycle for LED > > Yes, I was thinking an L-C circuit to boost the voltage at least. > > LTspice can be downloaded for free from www.analog.com > > I suggest you get it. > > boB >
Ya, I had it for a while played with it had fun with it, I did some circuits, went out and got subcircuits, all was cool and as I recall I was trying to show how match was important to power transfer nothing major just maximum power transfer, I posted it here got a shit load of flack, was told I need to learn electronics before I try LT spice. I just said Fuck it. Haven't touched it since. Mikek -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
On Sun, 31 Jul 2022 20:11:54 -0500, amdx <amdx@knology.net> wrote:

>On 7/31/2022 7:35 PM, boB wrote: >> On Mon, 01 Aug 2022 03:13:19 +0300, Klaus Kragelund >> <klauskvik@hotmail.com> wrote: >> >>> 31.07.22 22:58, jlarkin@highlandsniptechnology.com wrote: >>>> On Sun, 31 Jul 2022 10:56:27 -0500, amdx <amdx@knology.net> wrote: >>>> >>>>> I'd like to setup a high Q LC to receive a local Radio station probably >>>>> charging a cap, when the charge is high enough flash an LED. >>>>> Maybe set the trigger point of an SCR, or could just a zener do it. I >>>>> don't have LT spice, so please don't post and answer with that. >>>>> >>>>> Thanks, Mikek >>>> I expect that a strong radio station could light an LED visibly >>>> continuously, given a good well-matched antenna. Or charge a cap and >>>> use a discharge circuit to get bright blinks. >>>> >>>> Here's my high-voltage low current blinker: >>>> >>>> https://www.dropbox.com/sh/yaqbi52vbpo6uyc/AABPAczwj1zv26-fwI4LvJyha?dl=0 >>>> >>>> But LT Spice is free, easy to learn, and a wonderful tool for stuff >>>> like this. >>>> >>> Tuned LC with diode to big low leakage cap >>> >>> Then a BJT multivibrator, can operate in nA >>> Assign very low duty cycle for LED >> >> Yes, I was thinking an L-C circuit to boost the voltage at least. >> >> LTspice can be downloaded for free from www.analog.com >> >> I suggest you get it. >> >> boB >> >Ya, I had it for a while played with it had fun with it, I did some >circuits, went out and got subcircuits, all was cool and as I recall I was >trying to show how match was important to power transfer nothing major >just maximum power transfer, I posted it here >got a shit load of flack, was told I need to learn electronics before I >try LT spice. I just said Fuck it. Haven't touched it since. >Mikek
LT Spice will teach you electronics! And train your instincts. My office gets a gigantic RF field from Sutro Tower. I've been meaning to try to light an LED from that. A broadband match could scoop up an entire band, not just one station. When I was a kid, I had a crystal set with a germanium diode and hi-z magnetic headphones. On some stations, it was deafening. Had to be many milliwatts.
On Sun, 31 Jul 2022 19:54:46 -0500, amdx <amdx@knology.net> wrote:

>On 7/31/2022 2:58 PM, jlarkin@highlandsniptechnology.com wrote: >> On Sun, 31 Jul 2022 10:56:27 -0500, amdx <amdx@knology.net> wrote: >> >>> I'd like to setup a high Q LC to receive a local Radio station probably >>> charging a cap, when the charge is high enough flash an LED. >>> Maybe set the trigger point of an SCR, or could just a zener do it. I >>> don't have LT spice, so please don't post and answer with that. >>> >>> &#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080;&#2013266080; Thanks, Mikek >> I expect that a strong radio station could light an LED visibly >> continuously, given a good well-matched antenna. Or charge a cap and >> use a discharge circuit to get bright blinks. >> >> Here's my high-voltage low current blinker: >> >> https://www.dropbox.com/sh/yaqbi52vbpo6uyc/AABPAczwj1zv26-fwI4LvJyha?dl=0 >> >> But LT Spice is free, easy to learn, and a wonderful tool for stuff >> like this. >> >I was hoping to do it with just a coil and cap. I have some 6" coils with >Q over 1000. Very high impedance a resonance, so might need a lower >impedance pickup coil. >Their Litz wire, so I don't want to tap them.
You might consider a tuned loop antenna. What frequency stations do you have nearby?
On Sunday, July 31, 2022 at 6:12:02 PM UTC-7, amdx wrote:
> On 7/31/2022 7:35 PM, boB wrote: > > On Mon, 01 Aug 2022 03:13:19 +0300, Klaus Kragelund > > <klau...@hotmail.com> wrote:
> >> Tuned LC with diode to big low leakage cap > >> > >> Then a BJT multivibrator, can operate in nA > >> Assign very low duty cycle for LED
> > Yes, I was thinking an L-C circuit to boost the voltage at least.
That's important because the 'diode' isn't usually as sensitive as a crystal set (which has terrible breakdown, but good low-bias energy efficiency) Antennae have impedance, is matters what kind of antenna you connect.
> > LTspice can be downloaded for free from www.analog.com > > > > I suggest you get it.
> Ya, I had it for a while played with it had fun with it, I did some > circuits, went out and got subcircuits, all was cool and as I recall I was > trying to show how match was important to power transfer nothing major > just maximum power transfer, I posted it here > got a shit load of flack...
When you start using an LC tank, the 'maximum power transfer' trick of impedance matching becomes irrelevant, because the LC has a flywheel effect (doesn't lose energy just because it didn't deliver it to the capacitor). It also has free transformer voltage 'gain', but you'd want to use a tapped loopstick with sliding core to tune; that's a nightmare to characterize in SPICE parameters. You'd also want to slowly charge a capacitor to above-LED voltage, then abruptly discharge it, which is a transient that LTspice can handle, but only with amazing amounts of compute time. Using LTspice in that effort is excessively hard.
On 7/31/2022 10:04 PM, whit3rd wrote:
> On Sunday, July 31, 2022 at 6:12:02 PM UTC-7, amdx wrote: >> On 7/31/2022 7:35 PM, boB wrote: >>> On Mon, 01 Aug 2022 03:13:19 +0300, Klaus Kragelund >>> <klau...@hotmail.com> wrote: >>>> Tuned LC with diode to big low leakage cap >>>> >>>> Then a BJT multivibrator, can operate in nA >>>> Assign very low duty cycle for LED > >>> Yes, I was thinking an L-C circuit to boost the voltage at least. > That's important because the 'diode' isn't usually as sensitive as a crystal set > (which has terrible breakdown, but good low-bias energy efficiency) > Antennae have impedance, is matters what kind of antenna you connect. > >>> LTspice can be downloaded for free from www.analog.com >>> >>> I suggest you get it. >> Ya, I had it for a while played with it had fun with it, I did some >> circuits, went out and got subcircuits, all was cool and as I recall I was >> trying to show how match was important to power transfer nothing major >> just maximum power transfer, I posted it here >> got a shit load of flack... > When you start using an LC tank, the 'maximum power transfer' trick of impedance > matching becomes irrelevant, because the LC has a flywheel effect (doesn't lose energy > just because it didn't deliver it to the capacitor). It also has free transformer voltage 'gain', > but you'd want to use a tapped loopstick with sliding core to tune; that's a nightmare > to characterize in SPICE parameters. You'd also want to slowly charge > a capacitor to above-LED voltage, then abruptly discharge it, which is a transient > that LTspice can handle, but only with amazing amounts of compute time. >
&nbsp;I disagree with that irrelevant comment, you don't want to overload the tank, you want to keep the voltage up to stay higher on the diode slope, (so called knee). Tanks are tapped or coupled to reduce loading on high end crystal sets. Diodes are picked specifically to go with the Q of your LC. Coupling is often done by variable spacing between two tuned LC tank circuits. For any high end Crystal set, the LC, they are capacitor tuned not inductor tuned, that's fun but not used in high end units. Some crystal sets, have a separate LC tuned &nbsp;to a local station that charges a cap to power an audio amplifier for the audio when listening to distant stations. &nbsp; Sadly the best Crystal radio forum has died after the holder got Covid, had terrible health problems and the URL fee didn't get paid. Here is the mother load of Crystal radio study, done by Ben Tongue of Blonder-Tongue fame.
> http://kearman.com/bentongue/xtalset/xtalset.html
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Mikek -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus