(stupid session timeouts...lost my whole damn post!) grrr..
anyways..
thanks for replies.. to quickly sum up what I had origianlly typed out.
I 'do' want to use an Arduino.. (but in the end.. Im hoping to NOT take up 10 I/O pins to do so... (maybe a shift register?..going back to my other post...kinda works for same principle?)
@CR_
man you guys are just too smart/knowledgeable on this junk!.. Its another project just to decipher the answers! LOL
1.) Grumpy_Mikes comment.. (the meter itself is drawing excess current)... got it! Although I wouldnt have an clue nor cared without you guys pointing it out..
2.) I think your saying..I can cut that 'pull' of excess current down by... ?? 'adding'?? additional 4.7k & 10k resistors? (where?.. and additional?..not in place of...right?)
3.) I think your saying I should re-calculate my resistor values.. based on Vin of 8.4v and not 7.4v.......yes? (fully charged is more at 8.4v instead of 7.4v)
I think your saying..I can cut that 'pull' of excess current down by... ?? 'adding'?? additional 4.7k & 10k resistors? (where?.. and additional?..not in place of...right?)
By using resistors where you have them but making them ten times the value you have them.
I think your saying I should re-calculate my resistor values.. based on Vin of 8.4v and not 7.4v.......yes?
Hi, I have a problem also with a arduino voltmeter/ammeter that is part of a power supply I made.
I have written all the code connected it up and it reads the volts and amps pretty accurately on an lcd.
My problem is when i connect a load to the power supply the voltage drop shown on the lcd is no where near what it reads on a multimeter. ie. if I set the voltage to say 6.00 volts connect a 3.9ohm load the lcd shows 5.8 volts where as the multimeter shows something around 5.00 volts. and doesn't drop much more with bigger loads either.
Does anyone know why this might be?
thought the problem might be electrical but ill attatch the code for you to look at.
but I get about 1.1 amps when i do the maths there so its a little out.
cheers
#include <LiquidCrystal.h>
LiquidCrystal lcd(13,12,11,10,9,8);
// These constants won't change:
const int analogPin = A4; // pin that the sensor is attached to
const int ledPin = 6; // pin that the LED is attached to
const int threshold = 365; // an arbitrary threshold level that's in the range of the analog input
int analoginput0 = 3; //analoge pin 2
int analoginput1 = 4; //analoge pin 5
float vout1 = 0.0;
float vout2 = 0.0;
int value1 = 0;
int value2 = 0;
float R1 = 5100.0; // !! resistance of R1 !!
float R2 = 2193.0; // !! resistance of R2 !!
float vin1 = 0.0;
float vin2 = 0.0;
void setup(){
lcd.begin (16,2);
lcd.setCursor (5,0);
lcd.print ("G'day");
delay (1000);
lcd.setCursor (6,1);
lcd.print ("Mate");
delay (2000);
// initialize the LED pin as an output:
pinMode(ledPin, OUTPUT);
// initialize serial communications:
Serial.begin(9600);
// declaration of pin modes
pinMode(analoginput0, INPUT);
pinMode(analoginput1, INPUT);
lcd.begin(16, 2);
}
void loop(){
// read the value on analog input
value1 = analogRead(analoginput0); //voltage value
vout1 = (value1 * 4.555)/1023.0;
vin1 = vout1 / (R2/(R1+R2));
value2 = analogRead(analoginput1); //Amp output
vout2 = (value2 * 4.555)/1023.0; //4.555=voltage threshold (1023=4.555V);
vin2 = vout2*2; //vin2 = value2;
lcd.setCursor(12,0);
lcd.print(" ");
lcd.setCursor(8,0);
lcd.print(vin1+0.1);
lcd.setCursor(8,1);
lcd.print(vin2);
lcd.setCursor(0,0);
lcd.print("Volts");
lcd.setCursor(0,1);
lcd.print("Amps");
// read the value of the potentiometer:
int analogValue = analogRead(analogPin);
// if the analog value is high enough, sound alarm:
// if (analogValue > threshold)
if (vin2 > 3.2) // Set amp alarm value
{
digitalWrite; //(ledPin, HIGH); //ledpin for led
tone(7, 3);
delay(100);
}
else{
digitalWrite(ledPin,LOW);
noTone(7);
}
delay(100);
}
The 4.555 is the voltage I got when I measured the analogue input variable power supply and multimeter, so 1023 is reached at roughly 4.555 volts not 5 volts exactly, unless its the multimeter telling me different.
and I think i just added the *2 in there just to make the amps close to what it is ment to be. But yes i got a 0.5 ohm shunt on the ground rail.
Im no coding expert and just improvising where i can.
xl97:
So I will change out the resistors to be 4.7k & 10k respectively.. and lets me keep the draw form the 'meter' low...
but why @ a stable 7.4v from the PSU am I getting readings of 1023 from +5v - +7.4v??
My guess is that either the resistors you are using are not really 470 ohms and 1K (e.g. the one you think is 1K is actually 10k, or the one you think is 470 ohms is actually 47 ohms), or you are using one of those breadboards that has a break in the middle of the 5v and gnd rails and you haven't taken account of that break (so the 1k resistor is not connected to ground).
Yeh the 4.55 might be a bit low but at the end of the day i have to calibrate it to something and thats the reading i get @ 1023, its really no big deal i can change it to 5 but is less accurate, according to my meter. But its doesn't have anything to do with the voltage drop issue, or lack of it should i say.
Im still a bit unclear that even with the other resistors in place for a the 7.4v setting.. 'why' it didnt represent a 7.4v 'value' in the serial print?
I mean it was steady 1023 from +5v up to 7.4v..??
I understand why change the resistors.. (since in the end I'll be using 2 x 3.7v li-ions)..
but what was wrong with it currently.. at the 7.4v??
In my mind.. changing out these resistors will do NOTHING for me? (but are only to be put in place because in the end I'll be using a 2 x li-ions)
the question (for me) still remains and is unanswered..
WHY with the current set-up of resistors/voltage divder.. and a 7.4v source am I NOT getting any changes in my analogRea() from 5v to 7.4v?
xl97:
So I will change out the resistors to be 4.7k & 10k respectively.. and lets me keep the draw form the 'meter' low...
but why @ a stable 7.4v from the PSU am I getting readings of 1023 from +5v - +7.4v??
My guess is that either the resistors you are using are not really 470 ohms and 1K (e.g. the one you think is 1K is actually 10k, or the one you think is 470 ohms is actually 47 ohms), or you are using one of those breadboards that has a break in the middle of the 5v and gnd rails and you haven't taken account of that break (so the 1k resistor is not connected to ground).
sorry I missed this post.. (DOH)..
is there a way I can meter my resistors? to accurately find out the values?
or I suppose I could also try to look up the color bands? (always hate that)..