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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.
- 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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Signing UpStep 1Make some initial design decisions.
I had originally considered using a low-power 555 (the TS555) which claims a low operating current of around 150 micro-amps (0.00015 amps) at 9 volts. I had used a circuit almost identical to this one in project. If it was light outside, the light sensor D1 would have low resistance (around 100 ohms) and the reset pin would be near 0 volts, so the 555 would stay reset, keeping the output low. If it was dark, D1 would have high resistance (as much as 10 megohms) and R1 would pull the reset pin to nearly 5 volts and the 555 would run normally, blinking the lights.
However, even with 150 micro-amps all the time, a 9 volt battery with a capacity of around 540 milliamp-hours would last 3,600 hours -- about 5 months. I'd hate to install a brand new battery, use the bike a couple times, and have to replace it twice a year.
One option was to use a switch, but I wanted to make the light automatic.
However, even with 150 micro-amps all the time, a 9 volt battery with a capacity of around 540 milliamp-hours would last 3,600 hours -- about 5 months. I'd hate to install a brand new battery, use the bike a couple times, and have to replace it twice a year.
One option was to use a switch, but I wanted to make the light automatic.
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But in reality, no more transistors are needed, the original circuit (without the 555) has enough transistors so that it can be made into a standard two transistor flasher circuit. For circuit ideas, see:
http://www.techlib.com/electronics/flasher.html OR
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#flash2.gif
p.s. you might attract more people by making a catchier title
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.
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.