audioguru2
- Apr 6, 2004
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- Apr 6, 2004
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- 12,026
Hi Pier,
Many years ago I made an analog version of this programmable project. I used 3 very slow oscillators at slightly different frequencies making triangle waves. They drive transistors that drive red, blue and green LEDs. The LEDs slowly brighten and dim at their different frequencies and create every colour possible plus every brightness of every colour including black and white.
I used ultra-bright LEDs but if you use these high current LEDs then you need to use power transistors like the TIP31, and reduce the value of the 100 ohm resistors for higher LED currents.
My circuit was similar to the Fading Red Eyes project that is half-way through this link:
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm
Many years ago I made an analog version of this programmable project. I used 3 very slow oscillators at slightly different frequencies making triangle waves. They drive transistors that drive red, blue and green LEDs. The LEDs slowly brighten and dim at their different frequencies and create every colour possible plus every brightness of every colour including black and white.
I used ultra-bright LEDs but if you use these high current LEDs then you need to use power transistors like the TIP31, and reduce the value of the 100 ohm resistors for higher LED currents.
My circuit was similar to the Fading Red Eyes project that is half-way through this link:
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm
audioguru2
- Apr 6, 2004
- 12,026
- Joined
- Apr 6, 2004
- Messages
- 12,026
Just use a single type of transistor. Then you can change the bias voltage of the opamps so that each LED dims completely.
A BC547 has a max current allowed of only 100mA. A 2N3904 has 200mA. I used 2N4401 which has a max current of 600mA. Any will work with ordinary LEDs since their max current is only 30mA. The parts in the circuit limit the LED current to about 13mA.
The European BCxxx small transistors have their pins layout reversed from the American small 2Nxxxx transistors.
A BC547 has a max current allowed of only 100mA. A 2N3904 has 200mA. I used 2N4401 which has a max current of 600mA. Any will work with ordinary LEDs since their max current is only 30mA. The parts in the circuit limit the LED current to about 13mA.
The European BCxxx small transistors have their pins layout reversed from the American small 2Nxxxx transistors.
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