Semaphore and 555 Timer Circuit

Hopefully the following was just a "typo" and the 10uF is indeed hooked up properly.

Sharp eye Stan, that will certainly screw up the 555 circuit!

Here's the corrected files, the input file for TinyCAD and a graphics file for printing for those of you that don't have TinyCAD (which is free, FYI)

Edit: Added the missing ground that Stan so generously pointed out.

Not to be picky but I think pin 1 want to feel the love from Ground.

Duh, you're right, I was so busy moving the cap that I didn't actually look at the 555 data sheet.

I'll correct the corrected post files.

So in looking around in eBay for 555 timer modules, I came across this $1.27 (free shipping) module that has a 555 and 4017 in the same configuration as the Traffic Signal controller and the Knight Rider circuit.  Yes, you'd have to be handy with the soldering iron to modify the 10 outputs with the diodes and actual LEDs but it may be a way to save some time wiring up the 555 and 4017 portion of the circuit.  It probably runs fast for a traffic signal so the 1uF capacitor C1 would need to be increased.  Just a thought.

http://www.ebay.com/itm/New-NE...;hash=item4ad99b4138

One more thing on the 555.  Usually, if pin 7 (Discharge) is used for a basic oscillator, then the 500K pot goes to pin 8 (Vcc) rather than to pin 3 (output).  But there are zillions of ways to hook up the 555 - but I'd double-check that connection.

Looks like the designers found this diagram first.   There are a lot of ways to make the chip oscillate, I suspect you could wire it a ton of different ways.

Thanks for all the help guys (I need all I can get), I found the pin 1 and cap in wrong place error last night and I think my 555 timer circuit is still the culprit. Your last two posts (stan & grj) look promising. I haven't fiddled with it again yet today, but those suggestions are going to be coming up this afternoon. I must also check out the link stan posted, might have to have one or two of those. I am weak, I can't resist these things...

I think I must have copied from something else in the Tinycad drawing and never finished revising it? I was doing this about the time we started looking for a new house and moved a couple years ago. I can't find my original that I started with though.

Here's a search of Google Images for 555 Basic Oscillator Circuit, just look at a few of these and adjust your circuit until you have happiness.

So many circuits, so little time! I discovered something else a while ago.

With power on at 9vdc, I pulled 33k the resistor off of the 555 pin 3. It started working with just me holding the resistor and the other end still connected to pin 14 on the 4017. It was a bit fast, but at least I'm hot on the trail. Maybe I'll just discard the 555 and hold the resistor, a human timer...

The high impedance of the counter input was just picking up the 60hz noise, same thing you see if you grab a 'scope probe.

Problem solved, working now. No more human timer required, back to the 555. Works perfect if you get everything just right.  

I will fix the drawing and re-post sometime tomorrow.

Thanks to everyone for the assistance.

How close were we with the last drawing I posted?

Actually I think the only thing that was wrong was the cap on pin 1 instead of where it belonged, after pin 2 & 6. Pretty sure the real problem was my poor eyesight (cataracts they won't remove yet, maybe in a couple months) and I just had a jumper in the wrong spot and didn't (or couldn't) see it. (Not knowing what I am doing may figure into the equation as well. ) Must have checked those 555 jumpers at least a dozen times.

I did 2 things yesterday, tried a new 555 chip then took all the jumpers off the 555 and re-did them. I also changed the power to the 500k pot from pin 3 directly to power supply as Stan posted above. I now think the other 555 is fine though, never saw any magic smoke.

I am going to take it all apart later and re-do it to make sure my drawing is correct now, but I think yours where you moved the cap is also correct. I will try powering the pot from pin 3 again and see what happens when I re-do it later. 

If you would, post the corrected files, I keep them in the archives when this question comes up again.

I certainly will, later this evening. It might be me asking the questions again

Here is a clean file of everything, parts and revisions. For some reason the TinyCad files print funny now, won't all fit on one page. They are fine if you print from the pdf.

The Knight Rider did work with power to the pot from pin 3 of the 555, but I changed it to the main power source just to be on the safe side per Stan's post above.

In the Knight Rider Flasher, why does the 500k pot have a comment "Good starting point 4k ohm"?  Sounds like a big variance.

I left a lot of adjustment room there.   Actually that's the smallest one I had, 1M was the only other size I had. 4K was the only time I measured it. I'll fiddle with it some more and see if I can narrow that down a little.

I found the comment curious when I saw the component.

FWIW, when you're drawing something like this and you know the right component is, say a 10k pot, and you're using a 500k because you have one in the junkbox, I'd still make the schematic indicate the correct value.  Most folks that are going to try to duplicate it should know that you can use a larger one and simply not use the full range.

Good point, I'll remember that. Haven't had a chance to test the values again yet, but will post back with an updated diagram when I can.

Just so you don't think I forgot, my wife's father (86) is in pretty bad shape in the hospital, started very early yesterday morning, might be a while before I get back to the flashers.