555 tester

Here's a line following robot built with three 555 timers.  Since you have 80 of them surely you can spare 3 for this project. ? 

Article here: Line Following Robot using 555 Timers

For some reason the pictures in the article wouldn't show up in my browser.  But I just right-clicked on them and chose "view image" and I was able to see them.  I posted some of the images below including the schematic.

Parts List

1. 1k x (4), 4.7K & 180R
2. Potentiometers 10k x (2)
3. 10uF x (3)
4. LDRs x (2)
5. Bright White LEDs x (2)
6. n4148 Diode 
7. Transistors BD3904 x(2)
8. 555 Timers x (3)
9. DC Geared Motors (2)
10. 9v Battery

@ve1dx

Here's 40 more projects using the 555 Timer

@ve1dx, @robo-pi

Some time ago I was messing around with 555 timers and my then brand new oscilloscope and I discovered the following:

Although the datasheet quotes a voltage range of 5 to 18V, to get anywhere near the nominal frequency, you have to use 9V+.

I had built a circuit to give me a nominal frequency of 218Hz using the formula (0.694 x R x C) and these were the results I found.

Considering that the film resistors commonly used by us hobbyists are +/- 5% the nominal value and that electrolytic capacitors are a whopping +/-15%, that must account for the 7Hz difference between the calculated frequency against the actual measured frequency. Unfortunately, I didn't have one of those $13 component testers at the time.

A Ding Dong circuit.  Click on the schematic to read the full article.

Electronic Piano or Organ  click on schematic to read full article.

3 x 3 x 3 Electronic Cube click on schematic to read full article.

Electronic Mosquito Repellent - I wonder if this works?  I could use this in the summer!

Electronic Dice

This stuff reminds me of my childhood days. ? 

Electronics is so much fun.  It's like being let loose in a candy store.

@pugwash @robo-pi

Thanks for the circuits, 555 "lack of stability/consistency" analysis, @pugwash.  I will look at the circuit links that @robo-pi posted.  I agree that they are almost certainly unsuitable for a stable clock or oscillator.  Great for flashing LEDs, though, or other non-time critical applications.

In today's world, their best use is probably for learning basic electronics.  Both are forgivable of many mistakes, inexpensive, and the fact they've been around for about fifty years indicates they still are in high demand.  As @robo-pi and I discussed a few months back, having a drawer full of 555s and 741s are sort of essential for the electronic hobbyist.  Sometimes you want a quick and not too accurate circuit, and these chips do the trick.

I learned my basic electronics (still very rudimentary) about 45 years ago with 555s and a little booklet someone (Signetics?) put out with simple circuits using those chips.  When I burnt them out, as I regularly did, they were cheap to replace.  I still have a breadboard with a melted imprint of the DIP 8 package from one of my short circuits to remind me that mistakes happen often!

Paul VE1DX

Posted by: @robo-pi

Electronic Mosquito Repellent - I wonder if this works?  I could use this in the summer!

It's hard to say.  I saw some gadget that looked like a wall wart and supposedly repelled insects (and rodents) by emitting tones like that.  I was tempted to get one, but almost every review said it didn't work.  I ended up getting one of those upper body mosquito nets.  They work and save you from going 100% insane planting carrot seeds while feeding those critters.

If I were convinced it would work, that circuit stuck outside, would be a blessing.  I dislike mosquitos more than words can describe. ? 

Paul VE1DX

Posted by: @ve1dx

It's hard to say.  I saw some gadget that looked like a wall wart and supposedly repelled insects (and rodents) by emitting tones like that.  I was tempted to get one, but almost every review said it didn't work.

I actually bought one of those for "rodents" (in my case it was squirrels), not sure if a squirrel qualifies as a rodent?  Probably does.  I'll have to look up the definition of "rodent"

Rodent - a gnawing mammal of an order that includes rats, mice, squirrels, hamsters, porcupines, and their relatives, distinguished by strong constantly growing incisors and no canine teeth. They constitute the largest order of mammals.

Yep squirrels are on the list.   So are porcupines.   I never thought of a porcupine as a "rodent'.

Anyway I had flying squirrels living in my attic.  I didn't want to kill them by setting rat traps.  And I tried removing them using box traps and just letting them loose miles away.  The problem was they kept coming back (probably different squirrels).  For some reason my attic seems to attract flying squirrels as a place to breed.

Long story, shortened:

At night when I would go to bed I could hear the squirrels running around in the attic.  They can be extremely noisy!  Sounds more like raccoons having a fight.

In any case, I broke down and bought one of those ultrasonic pest repellers that are supposed to put out a high-pitched ultrasonic sound that the rodents can't stand.  I put that in the attic and it worked!  I never heard the squirrels again after that.  Whether it would work on mosquitoes I don't know.  But it works to chase away flying squirrels.  ? Supposedly it would also chase away mice too.

Getting back to my the mosquito problem.   In the spring and summer if there is a lot of rain, we can have a serious problem here with a very tiny species of mosquito.   These things are nearly microscopic in size.  You can just barely see them as tiny black specs and even then only when they are in large groups which they often are.

They seem to also have a tendency to be attracted to human eyeballs.  As they tend to fly directly into your eyes.  It's disgusting and extremely annoying.  I don't know what the species name is for these tiny mosquitoes but locally here they are called "punkies". 

Darn I had to look up punkies on Google and by-golly I found a definition:

(plural punkies) (US) A small two-winged fly or midge of the family Ceratopogonidae, which bites and then sucks the blood of mammals; the biting midge.

In any case, they can be extremely annoying.  As you say, wearing netting when they are around is paramount.  Fortunately I used to be a bee keeper and still have my bee keeping veil.

But wearing a net over your head can be a real pain too.

So if an ultrasonic device could be built that you could wear on a hat, that might just be the ticket.  If it actually worked to repel the punkies!  Might need to wear a 200 watt amplifier on your hat too. ? 

It might actually work if it's a powerful enough ultrasonic blast.

Posted by: @robo-pi

In any case, I broke down and bought one of those ultrasonic pest repellers that are supposed to put out a high-pitched ultrasonic sound that the rodents can't stand.  I put that in the attic and it worked!  I never heard the squirrels again after that.  Whether it would work on mosquitoes I don't know.  But it works to chase away flying squirrels.  ? Supposedly it would also chase away mice too.

Since we're getting into topic drift (not a bad thing, in my view), thanks for a review that can be trusted. I am glad to hear those things do work, at least for rodents. Happy to hear that you are now squirrel free! While they are cute and more or less harmless, they will drive you crazy with the noise if they get in the house. My father used to cuss them for stealing bits of food and stockpiling it in the dresser drawer in the 1960s. I think he kept throwing it out, and they got discouraged and moved away. It's excellent to hear from someone who isn't biased by a free sample or works for the seller.

I can report that the more complex ultrasonic and flashing light gadgets designed to keep cats from using your garden as a litter box also work. I bought two last year and no more kitty problems. The cats were unharmed and went elsewhere to the best of my knowledge.

They don't work with deer. This looks like it was a stuffed animal (or a photoshopped image.) Not the case. I took the picture out of my window, and he hung around for 5-10 minutes. I'd just finished harvesting the carrots in early October, and this fellow showed up. A couple of years earlier, one ate all the tops off of them. Oh well. We have to live in harmony with nature.

Paul VE1DX

Posted by: @ve1dx

Beautiful picture.  You couldn't ask for a better pose. ? 

I also live in a rural wooded area so I see visitors like this all the time.   I also live next to a state park so during the summer months there are a lot of campers driving by.  They often are spotting for deer.  I was thinking about buying one of those stuffed deer statues and rigging it up with a spot light held up by one front leg.  Then have a light sensor on it so when people spot at the deer the deer turns on its spotlight and spots back at the humans.

If I did that it would most likely become a tourist attraction.  Word would get around and everyone would come to my garden to see the deer that spots back.  Not sure if I want all the traffic. ?