5 replies to this topic

[bionicmotronic]

Folks: i have a project where i want to use a Netduino sense voltage on 10-12 lines that each could possibly go as high as 13-14V. I know exactly how i could setup voltage dividers myself to scale this down to 3.3V but id really like to find a somewhat affordable existing device or devices to save me the trouble of fabricating something so basic 10-12 times. I have seen some single signal tiny voltage sensor boards in the $6-8 range intended for arduino etc. applications that will work, but itd be even better if i could find an inexpensive single module w an array of 10 or more inputs / voltage dividers - just like you can find boards w an array of 8 output relays for controlling servos or motors... But for voltage inputs. Anybody know of anything like this? Or alternatively any cheaper-than-$6-per-analog-input solutions? Thanks in advance...

[hanzibal]

Hi! Why not multiplex the 12 using only a single voltage divider and analogue input? You'd have to sample 12 times as often but it would be very economical... About the relays, pretty much the same deal or use a latched shift register. EDIT: Your avatar looks like a turbo charged in-line four jap motor or an old BMW M3, but what is it? EDIT: If its for a motronic application, speed could be a problem.

[bionicmotronic]

Hi!

Why not multiplex the 12 using only a single voltage divider and analogue input?

You'd have to sample 12 times as often but it would be very economical...

About the relays, pretty much the same deal or use a latched shift register.

EDIT: Your avatar looks like a turbo charged in-line four jap motor or an old BMW M3, but what is it?

EDIT: If its for a motronic application, speed could be a problem.

 

Thanks for resply Hanz.   In order...

 

• That sounds like a fine idea, but what would I Mux w/?  An external mux IC that could handle the voltage if I understand you right?  If so I'd still need some suggestions of what to look at to do that...
• Ha. Not quite. Hint - "the other Bavarian"  
• Bing yes is for a Motronic application, however it is NOT realtime running-engine issues so  precision and speed doesn't have to be immaculate - I know Netduino isn't ideal for that. I already have a rig I built for rudimentary booting and logging into and limited output tests of old OEM ECU's but I really want to be able to monitor the output lines and basically log the triggers to confirm that the various drivers have basic function and report voltage output for each.

Any specific suggestions / ideas would be great - again some outputs will be as much as 13.5 volts... and speedwise something like a simulated 2k RPM signal would be at most say ~33-50hz (and often the signals will be 1/2 that - ~16-25hz aka 4 stroke engine with various triggers occuring only 1/2 the revolutions) so really super slow as far as even a weak micro is concerned... 

[hanzibal]

Yes, the general idea was to use an analogue multiplexer that can handle the voltage and then a single voltage divider between that and the Netduino. The CD4067B 16 channel mux/demux can handle up to 20V but Vcc must also be 20V:

 

http://www.ti.com/li...ink/cd4097b.pdf

 

If 20V is not readily available you need a step-up converter from 12V which infortunately would increase cost. On the other hand, such converters come quite cheaply on eBay:

http://www.ebay.com/...=item1c33d18e42

 

If you spend some time searching, you might be able to find a demultiplexer that can handle input voltage significantly greater than Vcc and then of course you won't need the converter.

 

Audi?

[bionicmotronic]

Thanks Hanz. Will look into that. Sounds like great solution. Will look into that.  (yep old Audi I5 20V) 

[hanzibal]

It suddenly hit me that you need an analogue switch instead of a multiplexer. There are many but this one is a 16 channel switch that can deal with 230V signals. I don't know but they could be expensive.

 

http://datasheets.ma...05-MAX14806.pdf

 

EDIT: Here's an overview from Texas Instruments:

http://www.ti.com/li...5d/slyb125d.pdf