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solid state "throw switch"

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tom86951

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I am not an engineer, so bear with me. I am looking for a solid state device to switch between two signals -- I have two 0-5vdc sensors and am trying to find a device/circuit I can connect them both to, such that the output of the device/circuit is either one sensor or the other, depending on whether a third control signal is either high or low. I presume this is simple stuff, but I am a bit clueless. Thanks.
 
8-pin DIP Mosfet relay with NO and NC sections, available form Digikey for about $5US.

http://pewa.panasonic.com/pcsd/product/pmos/pdf_cat/aqw61_eh.pdf

Hook a resistor and the two LED's in series, and whatever logic to switch LEDs. Tie pins 6 and 8 together as output and 5 and 7 as the inputs. The on-resistance is 1Ω. Would that be a problem? I've used this with a 10 bit ADC with no problems.
 
SYE said:
Hi,
I think these are probably the sort of thing your looking for.

CD4066
74HC4316


Stig.

Those may be what I am looking for, but I am just too unfamiliar to see it. What I want is feed two 0-5vdc sensors into a circuit and have the circuit output the signal from one or the other sensor, depending on whether a third control line is either high or low. Do these chips do that? They looked more like on/off switches controlled by the control line, or am I missing it?
 
tom86951 said:
I am not an engineer, so bear with me. I am looking for a solid state device to switch between two signals -- I have two 0-5vdc sensors and am trying to find a device/circuit I can connect them both to, such that the output of the device/circuit is either one sensor or the other, depending on whether a third control signal is either high or low. I presume this is simple stuff, but I am a bit clueless. Thanks.

Darlington driver IC's (ULN2801) could be your answer, depending on your output state, please see attachment.
 

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  • datasheet.pdf
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Thanks all. I'm sure I am just too inexperienced to see how these devices do what I'm after. I am not trying to switch anything with lots of current. Here is the issue -- I have an air flow sensor that produces a signal from o to 5vdc, depending on air flow. More flow, more voltage. That signal is used by my car's computer to meter out the fuel, etc. Separately, the car has a switch that goes to ground when the throttle is closed (and goes to 5v whenever the throttle is not closed). I want to intercept the air flow sensor wire and condition it so that (a) it simply follows the sensor voltage whenever the throttle is open, and (b) follows the sensors voltage when the throttle is closed, but only up to 1vdc. In other words, I want it to be a simple voltage follower whenever the throttle switch is high, and when the throttle switch is low I want it to be a voltage follower with an upper limit of 1vdc (so that if the sensor has .5vdc, the circuit will output .5vdc, but if the sensor has 1cdv or higher, the circuit will output only 1vdc). Suggestions?
 
Why do you want to mess with your car's fuel injection? Car engine computers are pretty well optimized to give maximum efficiency and power. Anything you do will likely foul that up.
 
crutschow said:
Why do you want to mess with your car's fuel injection? Car engine computers are pretty well optimized to give maximum efficiency and power. Anything you do will likely foul that up.


It is a highly modified motor (just under 500 horsepower 4 cylinder). The engine management works perfectly, except in one specific circumstance which I want to over-ride.
 
tom86951 said:
It is a highly modified motor (just under 500 horsepower 4 cylinder). The engine management works perfectly, except in one specific circumstance which I want to over-ride.


O.K....now that's a little more than I expected, search for whatever make/model of your car or consult one of the many high performance auto mod shops, chances are someone has already covered this modification?

ECU firmware is available on model/performance/specific tweak etc....

**broken link removed**
 
Attached is a schematic for the mosfet solid state relay that I suggested and the CD4066 quad analog switch suggested by SYE. Hope this makes it clearer.

Ken
 

Attachments

  • Mosfet SPDT Relay.gif
    Mosfet SPDT Relay.gif
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Last edited:
KMoffett said:
Attached is a schematic for the mosfet solid state relay that I suggested and the CD4066 quad analog switch suggested by SYE. Hope this makes it clearer.

Ken

Thanks very much for doing that schematic -- I was struggling to come up with the 4066 version, but now see the logic clear as day. Thanks again for that, and to all who responded! I'll experiment and report back. :)
 
tom86951 said:
Thanks very much for doing that schematic -- I was struggling to come up with the 4066 version, but now see the logic clear as day. Thanks again for that, and to all who responded! I'll experiment and report back. :)

hi Tom,
While you are experimenting, check out the HEF4053 analog selector.
 
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