Electronic design
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From: Paola, KS
Electronic design
I need a circuit that when turned on will give a one pulse output for 12vdc.
I also need a circuit that when given the pulse will turn on a relay with an adjustable 1-5 second timer.
I also need a circuit that when given the pulse will turn on a relay with an adjustable 1-5 second timer.
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From: Paola, KS
Electronic design
Thats pretty funny. My dad gets a circuit diagram of exact values of resistors and capacitors with a 555 timer to do what we want. Okay now that is all good.
So he takes it to our local Radio Shack and goes to the counter and says "I need all of the parts on this paper" the kid takes the paper looks at it, takes it to another in the store comes back and tells my dad "We are sorry sir but, we don't carry autmotive parts here" my dad says "those are just common electronic parts" they then say "oh those kind of things are over here" and my dad gets what he needs on his own.
I think it is kinda funny that anymore people at Radio Shack are just salesmen with no electronic knowledge whatsoever.
But you had a good idea, if there were people in there that should be they could have got us the parts and told us how to do it. I have the working peice on the workbench now.
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From: San Rafael, NM
Electronic design
What you are lookin for is called a "MonoStable Multivibrator" and can be wired up on the LM555 8 pin timer chip. Try http://www.uoguelph.ca/~antoon/circ/monovib.htm. Try adjusting the values of R1 and C1 for the different times desired. Use the formula (t=R X C) and don't forget the scientific notation for the capacitor when you are doing your calculations. Try using a potentiometer for R1 if you need to vary the length of time or for fine tuning. There is a lot of info on this on the web. Have fun!
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From: Paola, KS
Electronic design
What is the difference between a linear taper and a audio taper when taliking about potentiometers?
I have successfully made one that will output for about .5 sec. now I am going to try to make it adjustable.
I have successfully made one that will output for about .5 sec. now I am going to try to make it adjustable.
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From: Brea CA
Electronic design
It has to do with how much the resistance changed vs how much you turned the pot. A linear taper pot will change resistance linearly with the turn ie. turn the pot half-way and the total resistance changed by half. An audio taper pot is a special case, it changes resistance non-linearly. The taper is sloped to match the sloped response of the human ear which is non-linear. It is very close to a log taper. Hope this makes sense.
Barry
Barry
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From: Paola, KS
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From: Paola, KS
Electronic design
This design uses low voltage, low current dc to swith on and off high voltage ac, would it work with dc only (no ac in the load)?
<http://www.uoguelph.ca/~antoon/circ/solidstate.html>
<http://www.uoguelph.ca/~antoon/circ/solidstate.html>
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From: San Rafael, NM
Electronic design
A log taper basically means that it will taper in octaves. Since an octave scale is set up logrithmically. The human hearing tapers in octaves also so this will closely match the human ear.
As far as the load being high voltage AC, just make sure the relay is rated to handle the voltage applied to the switch. The concern here isn't so much the current going through the switch when it is closed(although that must be taken into consideration also), it is that you don't want to arch over the gap when the switch is open. The relay contacts tend to have very small gaps when disengaged and some electrons can jump the gap if the electromotive force is large enough. Try to get a relay that is rated 15% higher than the voltage you will be applying to it, this will minimize dammage to the contacts when actuating and ensure long life. unless otherwise stated, the relay AC voltage is in RMS.
As far as the load being high voltage AC, just make sure the relay is rated to handle the voltage applied to the switch. The concern here isn't so much the current going through the switch when it is closed(although that must be taken into consideration also), it is that you don't want to arch over the gap when the switch is open. The relay contacts tend to have very small gaps when disengaged and some electrons can jump the gap if the electromotive force is large enough. Try to get a relay that is rated 15% higher than the voltage you will be applying to it, this will minimize dammage to the contacts when actuating and ensure long life. unless otherwise stated, the relay AC voltage is in RMS.
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From: Paola, KS
Electronic design
There is no relay in the design it is just the name it is all solid state using a triac to switch the load. I did not know if the triac and bridge needed the ac to function or if it would work fine on dc.
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From: Brea CA
Electronic design
Jimmy, thanks for kicking this up, I forgot all about it.
Brian, a Triac will work fine on DC. In fact, a Triac is really just two SCR's wired back-to-back. The DC will go through the bridge ok too but there will be two voltage drops across the diodes.
Ya know Radio Shack has a solid state relay for $7. Switches up to 3 amps with a 1.2 VDC trigger.
Barry
Brian, a Triac will work fine on DC. In fact, a Triac is really just two SCR's wired back-to-back. The DC will go through the bridge ok too but there will be two voltage drops across the diodes.
Ya know Radio Shack has a solid state relay for $7. Switches up to 3 amps with a 1.2 VDC trigger.
Barry
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