Fake Meter/Dial/Gauge pin/needle activity

Hello community!

I hope you can all help me or tell me how stupid I am for not persevering with an extreme google, but I had a question I wondered if anyone can answer, or contribute some ideas/investigations in anyway.

Remember in the ole films where any dial or gauge or meter with a pin or needle would bounce with activity time to time? Either because of some immense power that they're measuring or just a pretty dial to show something electrical is alive?

Well I'm looking to reproduce this needle bouncing activity, preferably in an electric circuit way as I don't have the budget for a "Meter Fluffer" or whomever sits there at the back of the meter or dial with his hand holding the needle in place, or with some invisible wire.

Now, I don't have much idea on electrics or wiring leds or whatever myself, so something that is bare bones and simple would be appreciated.

If anyone still isn't clear about what I'm harping on about then do ask and I'll try and clarify!

Thanks for your patience

David.

I guess a good place to start is, when would you like this activated? Sound? Randomly? Then from there how can be figured out.

I have some thoughts on how you can do this, but I have a couple questions. Do you have a Volt meter or a current meter? Do you want the reading to constantly go up and down, or do you want it to briefly shoot up and stay low most of the time? Do you want it to go all the way to zero, or do you want some low reading that spikes? All of these options are relatively simple to do, but they require slightly different circuits, so it makes a difference exactly what you want.

I think he wants just a simple needle gage to jump back and forth like a reading.

Like this?


This is being driven via Arduino PWM interfaced to a PC showing different PC stat (HD activity, processor usage, etc). You could create a dummy routine using the Arduino to randomly bounce the needle. Depending on your meter, you may need to insert a resistor to make it range full scale. More details on your project would help.

Tutorial:
http://www.uchobby.com/index.php/2008/02/12/arduino-analog-gauge/

Code that I am using in the video:
int PWM_Out = 11; //We're using pin 11 but you can use any of the PWM pins (3,5,6,9,10,or 11)
int rxChar; //variable for storing characters coming from LCD Smartie
int controlValue; //variable for accumulating value to be shown on meter
int SetPWM(int value); //function that talks to the meter

void setup()
{
Serial.begin(19200); //open up a line to USB/LCD Smartie
pinMode(PWM_Out, OUTPUT); //Setup pin 11 for output
controlValue=0; //set accumulation to zero to begin
}

void loop() //start looping
{
if (Serial.available()) { //check if serial line is open
rxChar = Serial.read(); //read each character from LCD Smartie
if((rxChar>='A') && (rxChar<='Z')){ //check if the character is a letter
SetPWM(controlValue); //if it is, talk to the meter by passing the accumulated value
controlValue=0; //reset the accumulated value to zero
}
if((rxChar>='0') && (rxChar<='9')){ //check if the character is a number
if(controlValue>100) { //check if its over 100
controlValue=0; //if it is reset it to zero
}
controlValue*=10; //if its not, multiply it by 10 - assume if the value is 25, the
//first character(rxChar) is 2 but control value is still zero
controlValue+=rxChar-'0'; //now controlvalue is 2, the next time through it becomes 20 with
//the above step and the second character(rxChar) is 5 and it gets
//added to 20 to become 25.
}
}
}

int SetPWM(int percent) { //this function talks to the meter on pin 11
int valid=false; //variable to indicate whether call worked; set to false to begin
int pwmPin=0; //Set the pin variable to zero
pwmPin = PWM_Out; //Re-assign to PWM_Out
float pwmValue; //Declare a variable to hold the meter value converted to a percent
if (percent>100) { //If its over 100%...
percent=100; //...reset to 100%
}
if(percent<0) { //If its negative...
percent=0; //...reset to 0%
}
pwmValue=percent*(255.0/100.0); //PWM output is from 0 - 255 so this scales up the value
//Read this for more info http://arduino.cc/en/Tutorial/SecretsOfArduinoPWM
analogWrite(pwmPin,(int)pwmValue); //Writes the value to pin 11
valid = true; //Everything ok
return(valid); //Go back to the main loop
}

I don't understand that, but that's awesome. Great work.

Hi guys, thanks for the responses. As Mach has demonstrated, thats more or less exactly what I planned to do. Simple meter, make the need bounce around occasionally, no more than that really.

13doctorwho, this is actually intended to be for some dials/meters on a TARDIS console, but I thought I'd generalise the question should anyone else be searching for the same thing.

So I may need to invest in an Arduino, unless someone has a far cheaper approach. Any approach appreciated, just in case I have an Arduino doing other things!

The great thing about arduino is the sky is the limit. You can have it do meters and other things too.

Any one know where to get very tiny needle meters? Like 1/2 inch

If you want to use this as an opportunity to learn about the arduino that's great, but there are much cheaper circuits that can do the same thing. If I were doing it I would use a 555 timer to pulse the meter to get that effect. It can be done with literally $5.00 worth of parts. I, personally, don't like to program so a simple hardware solution is my preference. You can adjust the pulse frequency by putting a variable resistor in the circuit so you can vary the meter kick. One of the problems with an arduino is the limited voltage output. The older meters are usually higher voltage than the digital electronics of today.

By the way, I have built a TARDIS console myself, so welcome to the club!

davidnagel said:

So I may need to invest in an Arduino, unless someone has a far cheaper approach...

Click to expand...

I may have something for you. Ever seen the fake LED candles that flicker? I tore one apart tonight and found this inside. The candle was 3" in diameter, 4" high, and coated in wax. I dismantled a small tea light one (1.5" in diameter but no circuit board inside.)




I hooked it to a meter that I'm using for a PC build. I left the LED intact....just attached to the legs of the LED.



After adjusting using a 100K trimmer potentiometer, the meter would swing between 15 and 40 (3-8) as the LED flickered. This meter is a 0-0.2mA one but the same setup worked with a 0-1mA meter.



I soldered a header and the potentiometer to some veroboard and hot glued it to the back of the meter. I adjusted the pot until the meter was swinging mid range.

This is the pot that I used. http://www.digikey.com/product-detail/en/CT6EP503/CT6EP503-ND/738315



That's as cheap as I can come up with.

Nice one Mach, that's a handy thing to note next time I see some flickering led tea lights like that!

13doctorwho, the console I'm sprucing up is the Sean Clarke one which I'm documenting over at the tardisbuilders forum. Your console, by the way, is most superb.