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106  Using Arduino / Motors, Mechanics, and Power / Re: My sensor needs 18 ... 30 V DC.. on: August 21, 2013, 05:06:18 pm
ok, quick test.

make a voltage divider, two 250 ohm resistors in series.

    one end, to 5v, one end to ground, the middle to your analog pin,
        what do you read, should be constant,

I reckon you have a ground loop or a ground missing.

107  Using Arduino / Motors, Mechanics, and Power / Re: My sensor needs 18 ... 30 V DC.. on: August 21, 2013, 10:32:58 am
sounds about right
 

id go for the 200 ohm, dosnt have to be acurate, just predictable.
   if you have five of the 250,
     you could put two in parallel, to give 125 ohms
        and another three in parallel to give 83 ohms,
                 which in series gives 208 Ohms.

    near enough,
108  Using Arduino / Motors, Mechanics, and Power / Re: My sensor needs 18 ... 30 V DC.. on: August 21, 2013, 08:52:13 am
drop your resistor to 200 ohms,
    try that with the multi meter.


109  Using Arduino / Motors, Mechanics, and Power / Re: My sensor needs 18 ... 30 V DC.. on: August 21, 2013, 05:20:14 am
do you have a multi meter ?

disconect the arduino, supply power to the sencor, and put a resistor between the sencors output wire and its ground wire.

you should see a voltage across the resistor.

I need to draw a picture to show you whats required, which I cant do for a while,
110  Using Arduino / Motors, Mechanics, and Power / Re: My sensor needs 18 ... 30 V DC.. on: August 21, 2013, 04:22:37 am
nice sencor.

The analog output as mentioned, is specified as a current output.

The sencor varies the current out of the pin, between 4 and 20 mA depending upon range.

To detect a current with the arduino, one needs a voltage between 0 and 5v.

using ohms law, as mentioned above, 250 Ohms between the output pin and ground will give a voltage up to 5Volts.  If you go above 250 Ohms, then the sencor will output a higher voltage to give the 20 mA, which could blow the arduino,

Personaly I'd go for a smaller resistor, say 200 Ohms or even 100 Ohms, to give a lower impedance, less noise pick up, although less range into the arduino, and scale the arduino adc reading accordingly.

so stick a resistor between the signal pin and ground, gives u a voltage , that should be visible on a multi meter. On your picture your using Analog in 1 ? so your resistor is just fine, thought the gnd pin marked power is nearer,

out of interest, how much is the sencor ?
111  Using Arduino / Motors, Mechanics, and Power / Re: Thermoelectric Cooler & battery selection on: August 21, 2013, 04:06:43 am
was wondering how your getting on,
112  Development / Suggestions for the Arduino Project / Re: how about the STM32 on: August 19, 2013, 07:45:16 am
'just' have to port it to the arduino software,

:->
113  Development / Other Software Development / Exploring millis() on: August 19, 2013, 05:05:12 am
oops : Before coffee

I read it as multiply by 1024, i.e shift 10,
 
114  Development / Other Software Development / Exploring millis() on: August 19, 2013, 02:14:53 am
as its integer,
  and its a power of 2 multiply,
      just 'move the point' !

or have I miss understood
115  Using Arduino / Motors, Mechanics, and Power / Re: Electric Bike with Arduino UNO (48v-64v) on: August 15, 2013, 07:53:49 am
oops,

your right ,

I need more coffee !!
116  Using Arduino / Motors, Mechanics, and Power / Re: Inductive spikes protection? on: August 15, 2013, 07:41:54 am
if in doubt, put one on,

costs pennies, saves worries.
117  Using Arduino / Motors, Mechanics, and Power / Re: Electric Bike with Arduino UNO (48v-64v) on: August 15, 2013, 04:13:57 am
20 cells in series at 2.9 Ah each, gives a 2.9 Ah battery,
   you up the voltage in series,

so you will have 2000 watt or so of battery power available.
118  Using Arduino / Motors, Mechanics, and Power / Re: Thermoelectric Cooler on: August 14, 2013, 02:09:46 pm
have fun
119  Using Arduino / Audio / Re: How to do a DDS synth on Due with multiple waves. on: August 14, 2013, 01:29:08 pm
for referance,
   a dds only needs 1/4 of a sine wave,
      you generate the rest from the top two bits of the dds, to select which quadrant your in,

and the number of samples in the table you need is probably less than you think.
   think how you could interpolate between two values in the table...

this might be of interest.

http://www.analog.com/static/imported-files/tutorials/MT-085.pdf

 
120  Using Arduino / Motors, Mechanics, and Power / Li ion batteries on: August 14, 2013, 12:47:09 pm
dont know either of those two products, so cant comment.

if you miss treat NiMH, they might just catch fire, and smoulder.
    but thats unlikely.

Li Ion, if you hit a naked cell with a hammer they can explode.
  not the worst technology, Na cells are far more fun, but .

Dont put Li Ion packs in parallel, and you "SHOULD" be safe,
  
re metal case, dont you take that off to tinker with the robot ?
   wear a face mask.

BTW: those cells are 89 euro, which I think is about 90 dollars US,
    10 of them will give you 40 Ah at 34 volts.
       

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