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Author Topic: Switcher for Analog Inputs  (Read 2036 times)

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Offline jsmokerTopic starter

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Switcher for Analog Inputs
« on: June 28, 2007, 10:28:26 AM »
Does anyone know a solid state way to switch analog inputs sources? ie, switching between different sensors using only one analog input on a chip.  I figure it can be done with a relay, but I'm looking for something smaller and in solid state.  Does someone know of a chip that might be able to do it.  Optimally, it'd be awsome if someone might have heard of something for example like a 16 pin chip with like 8 inputs, 1 output, 3 pins dedicated to input selection and perhaps a power and ground pin.

On that topic, does anyone know of something that can change resistances in solid state with a digital signal?  Like a potentiometer only changed with a digital input rather than turning a knob.

The end going is that I'm looking to connect a bunch of strain gauges to a few inputs.

-Jason

Offline dunk

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Re: Switcher for Analog Inputs
« Reply #1 on: June 29, 2007, 04:51:16 PM »
Jason,
interesting question and i have to admit i don't know how you'd choose between analoge inputs.
the way i'd approach it would be to connect an inexspesive microcontroller (maybe one of the ATTiny series) to each sensor and connect them all together over an I2C or CAN bus.
this way your central microcontroller can request the reading from any of the other microcontrollers.
it might requre a bit of reading on your part though depending on your experience with microcontrollera/I2C.

dunk.

Offline hazzer123

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Re: Switcher for Analog Inputs
« Reply #2 on: June 30, 2007, 04:51:38 AM »
Ermmm i have found this - http://cache.national.com/ds/10/100364.pdf
But im not sure if it can handle analogue signals.

As for the digital potentiometer. They make these at Maxim-IC. Here http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2748

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Offline Soeren

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Re: Switcher for Analog Inputs
« Reply #3 on: July 01, 2007, 06:14:40 PM »
Hi,

Does anyone know a solid state way to switch analog inputs sources? ie, switching between different sensors using only one analog input on a chip.

The end going is that I'm looking to connect a bunch of strain gauges to a few inputs.
strain gauges are low ohmic, so using solid state to switch them would make them useless.

Besides, strain gauges needs to be used in a bridged configuration, followed by a differential amplifier to get useable results, if any kind of resolution and precision is needed.
The outputs of such amps could be fed into a 4051 (8 inputs) or 4067 16 inputs) analog multiplexer, but that'll still be a somewhat large PCB.
Regards,
Søren

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Offline KambeiX

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Re: Switcher for Analog Inputs
« Reply #4 on: July 01, 2007, 07:04:40 PM »
You can use simple logic IC plus switching transistors but it depends on what kind of output you are getting from the sensors.


Here is a very rustic example but it should work for readings between 0.7->5V translated to 0-->4.3




Offline Admin

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Re: Switcher for Analog Inputs
« Reply #5 on: July 11, 2007, 09:30:04 PM »
Quote
Does anyone know a solid state way to switch analog inputs sources?
Im guessing you want more than 8 analog inputs for your microcontroller? Perhaps you can get some of those analog to digital conversion IC's and attach them to serial or something . . .

Let me know how you end up doing this as Im always short on ADC ports myself . . .

 


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