LED strobes

[Nigel Goodwin]

I gotta defend myself. Better late than never. I was out seeking gold with my metal detector yesterday (found 2 little dinks).
Anyhow, my design works, unless I misunderstood the requirements. Here's the .ASC file for LTSpice.

You don't think that's perhaps a really useless format to post in?.

 

[Roff]

You don't think that's perhaps a really useless format to post in?.

No, because I posted the schematic previously. Torben said he couldn't get it to work in LTSpice. .ASC is the extension for LTSpice schematics. I posted it so he (and anyone else who wants) could run the sim. If you did simulations, you would probably know this.

 

[audioguru]

The simulation plays well when you click on a point to look at. I clicked on the output of the second 555 and it goes low 9 times then a pause then it goes low 9 times again then a pause again, over and over.

Years ago I made some very bright LED flashlights that do that, but the on time was very low to save the battery. I used two Cmos oscillators made from gates.

 

[Roff]

The simulation plays well when you click on a point to look at. I clicked on the output of the second 555 and it goes low 9 times then a pause then it goes low 9 times again then a pause again, over and over.

Nope. It runs once when you power it up, and then only starts a new cycle when you trigger it. Change .tran to 15, or 20, or whatever, and you'll see what I mean.

 

[Leftyretro]

No, thyristors are semiconductors - you 'may' be thinking of thyratrons?.

Your probably right, it's been 40+ years They worked like SCRs with a gate voltage that caused ionization to trigger causing the tube to conduct hard on. Had a 4 digit military tube number like 6360 or something like that. Glowed kind of cool like when conducting.

Lefty

 

[audioguru]

I run it and nothing happens until I click on a point to look at.
When I click on the output of the second 555 there is a 2 seconds pause then the output goes low 9 times then continues pulsing.

 

[Roff]

I run it and nothing happens until I click on a point to look at.
When I click on the output of the second 555 there is a 2 seconds pause then the output goes low 9 times then continues pulsing.

All is as it should be, I believe. It is also interesting to look at the timing capacitor voltage (C4) on the second 555.

 

[Torben]

I gotta defend myself. Better late than never. I was out seeking gold with my metal detector yesterday (found 2 little dinks).
Anyhow, my design works, unless I misunderstood the requirements. Here's the .ASC file for LTSpice.

Sorry Ron! I meant only that I hadn't figured it out, not that it wasn't a good circuit. I've seen enough of your stuff on here to know that this is more likely due to me not getting something right, not you!

I should've worded that better.

Anyway, I think maybe neither of us really understood what the original poster was asking for, since in one post he asked for a 3Hz strobe, in another post he asked for a strobe every 3 seconds, and in another for a duty cycle of 50%.

Now that I think about it, actually, I think he wanted a mix of what you and I came up with: the 2-second on pulse, then pauses of 3 seconds interspersed with 1-second 3Hz blinking. (blinkblinkblink. . .blinkblinkblink. . .etc). Hm.

And yes, the voltage C4 is very interesting. Is this related in some way to how charge pumps work, except more complicated and less efficient? [Edit: never mind; figured it out.]


Torben

 

[Torben]

Hi Torben,
Now your circuit looks good.

I have never seen a 500 ohm "standard" resistor. 470 ohms and 510 ohms are standard.

Heh. I knew I should've slept on it before posting. Also, the comment text in both of my schematics is wrong where it says the second 555 section pulses at 3Hz, when it pulses at 0.3Hz. *sigh*


Torben

 

[risp73]

Anyway, I think maybe neither of us really understood what the original poster was asking for, since in one post he asked for a 3Hz strobe, in another post he asked for a strobe every 3 seconds, and in another for a duty cycle of 50%.
Torben

Hi, excuse me please for "my english". What I need you can see in attachement.
I do not use LTSpice, attach schematics as .jpg, gif, png, ... please.
Tnx

 

[audioguru]

I expected to see a curved triangle wave on the capacitor.
SwCAD III thinks that the output of a 555 is rail-to-rail.

 

[Roff]

Hi, excuse me please for "my english". What I need you can see in attachement.
I do not use LTSpice, attach schematics as .jpg, gif, png, ... please.
Tnx

Do you want the circuit to do this only when power is turned on, or do you want to be able to start it with a trigger edge (or pulse)?

 

[Torben]

Hi, excuse me please for "my english". What I need you can see in attachement.
I do not use LTSpice, attach schematics as .jpg, gif, png, ... please.
Tnx

Hi again!

Don't worry about your English--it's better than what many native speakers use to post on the net. The problem is mostly just that there wasn't enough information to figure out quite what you wanted.

Also, you can safely ignore the .asc files (or you could download LTSpice; it's free from https://www.linear.com/designtools/software/). The one I posted was the same circuit as what you see in the PNG image that I also posted with it.

As Roff asked, does this need to work only once on power-up, or does it need to work on power-up and then whenever a trigger is received?

Also, what voltage does this need to work on? My circuit is assuming 5V; Roff's uses 12V. However, I think either should work with any voltage from 4.5V to 16V (those are the extreme edges of what a 555 will take)--just make sure that the current-limiting resistors are sized reasonably.

Anyway, here's a circuit that should do either. See the point where S1 goes to the left side of C5? All S1 is, is a normally-open switch to ground, and all it does is pull that point to ground for a brief time to retrigger the circuit. If you only need this to work on power-up, then get rid of C5, R3, R1, and D5, and it should work. (V2 is not a real thing in the real circuit; it just provides a quick voltage spike at 7 seconds to switch S1 to retrigger the circuit in the simulator.)

(Again to the wiser among us: please let risp73 and me know about any mistakes!)


Hope this helps,

Torben

 

[risp73]

... you could download LTSpice; it's free from https://www.linear.com/designtools/software/).
Torben

LTSpice is not there :-(

... As Roff asked, does this need to work only once on power-up, or does it need to work on power-up and then whenever a trigger is received?
Torben

Only once on power-on: PowerOn, 2 sec impuls, 3 Hz until PowerOff.

 

[Torben]

LTSpice is not there :-(

Did you get a 404 Page Not Found error? The ')' at the end of the URL I posted messes up the link, I guess. The link again, with no '()':

https://www.linear.com/designtools/software/

Only once on power-on: PowerOn, 2 sec impuls, 3 Hz until PowerOff.

OK, then the last circuit I posted should do the trick; just remove the components I mentioned in my post.


Torben

 

[risp73]

Thanks Torben. One question more: when you say LTSpice you mean LTspice/SwitcherCAD III ?

 

[Torben]

Thanks Torben. One question more: when you say LTSpice you mean LTspice/SwitcherCAD III ?

Yes sir, that's the one.


Torben