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721  Using Arduino / General Electronics / Re: Arduino Reading Multiple Sensors - Voltage Divider on: January 05, 2014, 05:48:08 am
What you say is correct...

Maybe I'm missing a really simply solution...

Requirement is:-

16 Rooms - Currently Max 10v dc output which is 100 degrees c.
I need to divide the voltage by 50% so its maximum for the arduino is not reached. (5v dc).

I dont want to use a voltage divider for every room (that would be using 32 resistors, as well as messy wiring / circuit board).

I want to use only 2 resistors to bring the voltage from 10v dc (100 degrees c) down to 5v dc for all rooms.

My program will change the values from if 5v dc then the temp is 100 c, if 2.5v dc then the value is converted to 50 c.





I don't believe there is an easier way (except using multiplexing)....

722  Using Arduino / General Electronics / Re: Programmer branching out, where to begin? on: January 05, 2014, 05:45:18 am
For a long time when I was trying to understand transistors I'd be confused over the roll of a transistor...

It took me a while to cotton on that a transistor  is like a swiss army knife, depending how you wire it, you can make it perform many actions...

A transistor can be used as a switch, it can be used to amplify, they can be used to regulate voltage, schmitt triggers can be made etc etc... once you get your head around that, the basic uses are easy to learn....

723  Using Arduino / General Electronics / resistor divider equation. on: January 05, 2014, 04:36:55 am
V = r2 / r1 + r2 * v

But could I use this instead (as it's easier for me to remember)

V =  V / R1+R2  * R2


They both give 6.6v  and 3.3v  (from 10v and 2 ... 10ohm and 20ohm resistors) but will I run into problems using this formula (yeah my math skils suck hard)
724  Community / Bar Sport / Re: Poor ad choice heading on: January 05, 2014, 02:02:51 am
What if you buy one and it turns out it stays cold!

False advertising?   smiley-eek
725  Using Arduino / Programming Questions / Re: Debounce toggle. Another stupid noob code question. on: January 05, 2014, 01:41:10 am
True, but being smart should mean you aren't a dummy. I think that's the point cjd was making.

Well, let me tell you... The "dummies" books aren't written for true dummies. Well, at least not this one. It's a book that talks down to the average reader using far too much programmer lingo.

Imagine me telling someone how to measure their house using points, picas, mutts and nutts. (I'll give you a hint, it's printing lingo)

I found it funny a self confessed genius reading dummies books, no insult intended.

Either increase the debounce delay, or while button state is high, do nothing like mike said but  is it really that much of an issue?

726  Using Arduino / General Electronics / Re: Ua 741 OpAmp how to connect it to get a gain of 2? on: January 05, 2014, 01:10:19 am
Never claimed it was... I was a bit confused by the question now I understand....
727  Using Arduino / Programming Questions / Re: Debounce toggle. Another stupid noob code question. on: January 05, 2014, 01:08:40 am
A genius reading a dummies book!

As for the code,  it's not very nice code, eg ledstate > 0  if LedState==HIGH (ie not 0 being false)

Debounce Delay, you say flickering, 250ms pauses before flicker?
728  Using Arduino / General Electronics / Re: Ua 741 OpAmp how to connect it to get a gain of 2? on: January 05, 2014, 12:54:39 am
It's a better alternative to a voltage divider... (just going from the resistor divider)

A split rail, check out this..

729  Using Arduino / General Electronics / Re: Arduino Reading Multiple Sensors - Voltage Divider on: January 05, 2014, 12:48:48 am
the below might be of interest.

https://www.sparkfun.com/products/9056


This is a cmos version, higher voltages would be an issue .
730  Using Arduino / General Electronics / Re: Ua 741 OpAmp how to connect it to get a gain of 2? on: January 04, 2014, 10:46:22 pm
An lm317 adjustable voltage regulator?
731  Using Arduino / Programming Questions / Re: !!! Push Button Counter !!! EASY ANSWER PLEASE HELP on: January 04, 2014, 10:32:33 pm
I'm not sure 10ms is long enough as your finger will still be pressed...


100-300ms is more likely to give better results, but delays make things appear laggy.
732  Using Arduino / General Electronics / Re: Arduino Reading Multiple Sensors - Voltage Divider on: January 04, 2014, 10:26:15 pm
Yup that pretty much is it ...


Someone might know of a 16 channel chip....  4051 is cheap and cheerful but it handles up to 16v (so careful which chip you pick)
733  Using Arduino / General Electronics / Re: Arduino Reading Multiple Sensors - Voltage Divider on: January 04, 2014, 10:00:31 pm
I guess you could use a multiplexer, feed all the voltages in to a chip, then you can cycle through each voltage in turn using the same 2 resistors to measure the temperature from all the sheds.

As a starting point to see what I mean take a look at 4051  datasheet.

734  Using Arduino / General Electronics / Re: Relay to turn on an inverter? on: January 04, 2014, 09:56:11 pm
I once did the same trick, keeping the relay energized in event of lack of power, the normally closed/open whichever springs to life...

But, the relay consumes power 24/7, also this inverter is powered how? 12v battery? In which case you don't really need an inverter unless you really like Christmas lights..
735  Using Arduino / General Electronics / Re: 5v to 3v logic... on: January 04, 2014, 09:49:29 pm
The reason for posting this is to find out if that circuit is safe to use ... eg I don't want to end up supplying 5v to the due.

If not  I'll use a zener 
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