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To Sebi: More flasher help needed, please.

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Hi Sebi,
Thanks for all your help. Sorry it took so long to say that.

Based on what you sent me about a single-NAND-gate flasher, I came up with the following schematic. I can't test it yet because I don't have the chip, nor does my circuit software simulate it properly. Will it work? I want to be able to flash the LED when both inputs go high. What do you think?

Sorry I couldn't PM this but it doesn't allow attachments!
 

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Nigel Goodwin

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captainkirksdog said:
Hi Sebi,
Thanks for all your help. Sorry it took so long to say that.

Based on what you sent me about a single-NAND-gate flasher, I came up with the following schematic. I can't test it yet because I don't have the chip, nor does my circuit software simulate it properly. Will it work? I want to be able to flash the LED when both inputs go high. What do you think?

Sorry I couldn't PM this but it doesn't allow attachments!
Interesting idea! - I'm not suprised it wouldn't work under the simulater though!.

I can't see it working where the transistor is, move the transistor so it's directly across the capacitor - emitter to ground, and the collector to the top of the capacitor. Put a resistor where the transistor was - it's not very good practice to have a pot wired like that without a limiting resistor. When the transistor turns on, it will then short out the capacitor, stopping the oscillator - when it's turned off the oscillator should run as is the transistor's not there. You will need to arrange the logic so that it works in that way.
 
Hi Nigel,
I like your idea, but it won't do what I need it to do. In my original post, I asked for a single NAND gate LED flasher. I had only one gate left and I didn't want to have to use a whole chip just for a flasher. (I know, I could just use a flashing LED--but that's not the point!) :wink: Anyway, I can't change the existing logic as it is used for other things. In a nutshell, what I want is when I get two logic-high levels at the existing AND gate, it drives the last NAND gate as a 1-2Hz LED flasher. Got anything in your bag of tricks?
 

Nigel Goodwin

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captainkirksdog said:
Hi Nigel,
I like your idea, but it won't do what I need it to do. In my original post, I asked for a single NAND gate LED flasher. I had only one gate left and I didn't want to have to use a whole chip just for a flasher. (I know, I could just use a flashing LED--but that's not the point!) :wink: Anyway, I can't change the existing logic as it is used for other things. In a nutshell, what I want is when I get two logic-high levels at the existing AND gate, it drives the last NAND gate as a 1-2Hz LED flasher. Got anything in your bag of tricks?
Just remove the second gate, feed the transistor from the first gate, via a limiting resistor - when the output is high the transistor would be on, stopping the oscillator, when it goes low it turns the transistor off allowing the third gate to start oscillating.
 
Nigel,
Do I need the resistor in place of the transistor? There is a 22k resistor already in series with the pot. Why can't this one suffice?
 

Nigel Goodwin

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captainkirksdog said:
Nigel,
Do I need the resistor in place of the transistor? There is a 22k resistor already in series with the pot. Why can't this one suffice?
Sorry, yes you don't need to bother (as soon as you click on 'Quote' you lose the picture!, so I was going from memory). Simply short the existing transistor position out, collector to emitter.
 
Nigel,
Thank you so very much! I appreciate the help.
 

Sebi

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Captain,

as i see You need some dual-flasher with AND input. I really don't understand why need a transistor? One logic output can drive min. 10 inputs in same family. Is this what You need? If both inputs are high, the two oscillator started.
BTW:Your cct with transistor can't work, because the driver voltage via 1k and emitter-base diode immediately charge the condenser full...
 

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