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The Smart, Stealth LED Blinkenlight

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My girlfriend has a nice old-school Schwinn Collegiate 5-speed bike. I would like her to be safer when we ride at night but I also wanted to maintain the vintage look of the bike so I decided to build a bike light for her. My goals are as follows:

- The light shall not affect the "stock" look of the bike.
- The light shall operate only when it's dark enough to be effective.
- The light shall operate automatically when the bike is in use and for around 30-60 seconds afterward.
- The light shall blink to enhance visibility at night.
- The battery on the light shall last "indefinitely" when not in use.
- The light shall efficiently utilize the battery's power when in use.
- The electronics of the light shall be reasonably weatherproof -- at least enough that road spray will not affect operation.

Based on that, I made the following initial design decisions:

- The light will use an existing bike reflector to maintain the stock look.
- The battery type will be a 9V rectangular battery.
- The light will use 3 2-volt red LED's for a 6 volt voltage drop. This will additionally allow a 8.4V rechargeable battery to be used in place of the 9V.
- A wire-through-a-spring will be used to detect vibration indicating the bike is in use. The spring will wiggle when the bike is jostled, making electrical contact between the wire and spring.
- A capacitor discharging through a resistor will be used to time power usage on the light for 30-60 seconds.
- A 555 timer will be used to provide make the lights blink.

P.S. In case you're wondering, I used EAGLE (the circuit design package from CadSoft) to lay out the circuits.
 
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bio882 years ago
nice - but why the hot glue and then the metal squares and then spring. Agreed it looks nice but you could have omitted the squares I'd think.
twocvbloke5 years ago
I've cracked open a spare (well, I have 3 already on my bike!!!) rear reflector to do something like this, only mine will just be a permanently on red light, though trying out an LED torch behind the reflector produces an interesting effect, instead of being directed directly behind the bike, the light is reflected out in 6 different directions, handy to let a passing vehicle know that you're there... :) My only problem is getting the resistors I'm using to fit under the reflector, I can shave down the LEDs, but I can't shave down the two resistors... :\ But, I'll cross that bridge as I come to it... :) If it fails, I'll just take a trailer foglight and fit a cr*pload of LEDs in there and attach it to my pannier's light bracket... :D
440hertz5 years ago
It's an interesting project actually, of course there are other ways to do it, but there usually are in electronics and most things in life. I don't agree that the 555 ciircuit is 'the worst', I've seen much worse, hey I've drawn some terrible circuits, LOL. Seriously though, pin numbers don't usually match the package, the diagram is usually drawn to look neat, makes it easier to read. I understand what is being said about 'instructables' being a place for novices, but there is a range of projects here, from simple to quite complex. You pick one at your skill level and with practice even the average joe will be able to tackle the more complicated ones. Learning is a good thing right?
mark1017 years ago
Worst circuit diagram of a 555 timer I have seen in my life! Congrads on confusing novice builders.
jolshefsky (author)  mark1017 years ago
So what in particular is wrong with it? It looks not only good -- at least as good as what I see in application notes on specification sheets -- but actually quite clear and expert? Any particular step you're talking about?
The steps are fine, I wrote "circuit diagram". The pins on the 8 pin chip , in reality are in totally diferent places. Why did you make the 555 with pins in an order that make the circuit diagram look good? 1234 on one side and 5678 on the other.
jolshefsky (author)  mark1017 years ago
Basically one reason: that is the way the pins were laid out on the package in EAGLE. In industry, nobody lays out circuit diagrams according to the pins on the package because it's a symbolic representation of the circuit. The only time the package comes into play is during the layout of a circuit board -- when you're dealing with physical components. That's what I did in Step 4. In the end, though, if it confuses you, you can always redraw the circuit with the pins in package-order.
"EAGLE" in all capitals doesn't mean anything to me, sorry.
I had to go to your link to find out what it is.

You wrote "if it confuses you". Very funny. If I was confused, I wouldn't have complained would I? My circuit just wouldn't work.

Calling it "industry design" doesn't make it easy to read.
Instructables are for the average Joe's that doesn't work in the industry.
Hence the reason why I called it the Worst circuit diagram.

The typical symbolic representation of the 555 is http://www.kpsec.freeuk.com/images/555ast.gif

and this page is what typical 555 circuits look like. http://home.cogeco.ca/~rpaisley4/LM555.html#7

To use a 555 for a blinking circuit is overkill , a simple push/pull two transistor capacitor circuit would have done the job.
Welp I guess you know what "EAGLE" is now.

Average Joes should learn to communicate in the language of electronics if they want to exist in it.

Seems some other inconsiderate people are trying to comfuse you! Here's an example : http://www.instructables.com/files/deriv/FIR/FMX4/EO8EQHO9OEH/FIRFMX4EO8EQHO9OEH.MEDIUM.jpg

Honestly I've looked at hundreds of schematics and they're all drawn up this way pin numbers don't correspond with package outlines. Not that I have seen.

If everyone jumped off a bridge...
How would you like them drawn? Smartie shaped, Amphibious Landing craft shaped, Poke in the eye shaped ?
Are you a troll, or can you not read? I linked to the way I would like them drawn Jul 9, 2007. 5:19 PM
"simple push/pull two transistor capacitor circuit would have done the job." How does that work exactly? I'd be interested to try...
parts list, is two transistors, two [same if you want 50% duty](10 to 47 uF) caps, 4 resistors >two 1 Kohm two 100Kohm , two LEDs, power 6 to 15 Vdc.
Jan20.jpg
jolshefsky (author)  mark1016 years ago
It all depends on what's in your parts box at the time. One 2N2222 transistor costs about $0.20 from Mouser; a LM555 timer costs $0.25. Capacitors run about 10 cents each; resistors are pennies. So the Push-Pull circuit — while "simpler" costs around $1 (without LED's) whereas the similar 555 circuit costs half that.
cool. Thanks man, i'm gonna have to try this
LOL theres not a thing wrong with it, I understand it perfectly well, this just isn't a project for beginners in electronics, I think the only way to make it easier for people who are new is just make the PCB files so they can order a circuit board of it from a place like BatchPCB. You can see the way I did my electronics section for my robot instructable here. Mine isn't a beginners project either, but I took out most of the skilled electronics work by giving people a way just to buy a professionally routed PCB. just my 2 cents

p.s. you might attract more people by making a catchier title
jolshefsky (author)  Brandon1212337 years ago
I'll try the new (hopefully) catchier name and see how it flies. As for PCB layout -- I decided to do it prototype-style so I didn't do a complete layout. The pseudo-layout I did do helped quite a bit although I had some trouble with the nets not being right. So in the end, I probably would have futzed around and ended up with a non-working PCB. :-)
rockyt7 years ago
I like this alot. I'm making one for my kid's bike. Thanks.