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Forum Index : Electronics : Pulse generator - Two (TTL)Signal Outputs
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vasi Guru  Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Can be useful on testing circuits based on microcontrollers (Stepper drivers, loggers, etc.). Is an old schematic, I can't remember from where I have It. I did it very long time ago, and it was one of my first circuits. The blinking frequency can be up to 17 beats per second. This is not for performance testing, but for functionality testing. It uses a 74LS00 but can be also a 74LS04 (but pcb must be redesigned - don't remember exactly the "pinouts" of 74LS04). The board can be powered from the microcontroller development/testing board. Maybe is useful for someone... 
Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| woodchips Newbie  Joined: 05/01/2009 Location: United KingdomPosts: 27 |
Vasi Surprised it works. Why not use a 74LS132 schmitt input NAND gate? That way the threshold voltages will actually cause the gate to switch and not amplify. Also using the gate output current limiting to drive the LEDS is a silly way of saving a resistor. I hope the 220uF cap isn't a tantalum? They seriously object to being reverse biassed, not at all pleasant when they blow up. And whilst I am moaning, can't we get away from having cicuits with signals joining at a cross. If they all join at a TEE then there is never any doubt as to wether there is a connection or not. Bob ps why not a 555? |
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| vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Hi, C1 is not tantalum. Why not a 555? Well, back in 1985-1986 74LS00 was very cheap. Still have a bunch of them. And it offers nice visual feedback with such a few components. [quote]Surprised it works.[/quote] It works nicely but if you want to use as a test circuit for PICAXE pulse count, then you must use optocouplers because the noise is big. Try it for fun  .
P.S. I'm not good at electronics 
I used it here: 
Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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