HELP me build a gas gauge????

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okay i will.... i had a slight glitch in R&D.....riding season the set of gauges i had for R&D had to be sent back to the owner until fall.... i will pick this up soon enough. here is a pic of the gagues so far(i have done the color modification, stock they are orange in color, then installed a gear indicator pcb that takes logarithm of mph and rev to compute 1-6 on the display) the 5 leds will be below the 7 and in a vertical bar, with the 6th behind the stock gas dumby light

**broken link removed**

**broken link removed**
 
Paralleling the outputs of linear regulators, is never a good idea because they all have slightly different output voltages and might fight each other.
 
 
Hero999 said:
Yes, the datasheet should provide all the information you need.
Click to expand...
excellent! i'm gonna fab this up this week. just have to wait till monday to get the 2v5 zener! it's going into a motorcycle insturment cluster. thanks!
 
Please bear with me as I'm a complete newbie, and haven't done any electronics since I was at School!! I've been looking through this post, and it seems to do almost exactly what I want, but I need a little help to get the details right:

I'm wanting to build an LED meter for a rainwater tank, using a MaxSonar ultrasonic distance meter and a LM3914. The MaxSonar gives an analog reading of approx. 9.8mV/inch, so when my tank is emty the distance will be approx. 70 inches, so 0.68v.

A couple of issues I need your expert help with please:
1. When the tank is full, the distance from the sensor will be small, so the voltage will be at its lowest. I therefore need to reverse the signal as in the Gas project above.
2. As the actual voltage range will depend on the final installation, I need to be able to adjust both the zero and range by say +/- 10 inches (98mV)
3. The sensors will be in the tank and the display in the house, so the cable to the sensors will probably be 15m long. Will a 5v supply pass down this OK, and in turn will the length of cable have any effect on the return voltage?

I've had a good look at this thread and the tech specs for the LM3914, but am really struggling to get my head around circuit diagram and the sizing of resistors.

Is anybody out there able to help me specify the Preamp and resistors, and work out a wiring diagram?

Many thanks in advance.
 
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Hello needlerp...
I have a small suggestion for a more speedy reply for you....
If you start a new thread with your own title and in it reference this thread so people know you've read it you are likely to get a much faster reply.

Hero and others have helped the original poster to a satisfactory result therefore it is done and dusted and they may not come back to this thread to see your question tacked on the end here....but a new thread with a new title will pique their interest probably...

...and I would be interested to see how this pans out as well....this forum is worth a thousand books...
 
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Thanks, I've done just that.
 
can i ask for help ?
i dont know much of eletronics i've been searching for a 90-0 led indicator with reserve led but i hadn't found anything can any one help me to convert this schemetic to a 90 ohm empty 0 ohm full prob??

thanks
 
Mind-Twist said:
can i ask for help ?
i dont know much of eletronics i've been searching for a 90-0 led indicator with reserve led but i hadn't found anything can any one help me to convert this schemetic to a 90 ohm empty 0 ohm full prob??

thanks
Click to expand...

You would do better to start a fresh new thread.

Ron
 
I have been scheming on using the LM3914 for a motorcycle fuel display for a while. This post seems to have amost everthing I will need, other than some newb clarifications I will probably have once I start breadboarding the proto. My concern/question is about real world function. the fuel in the tank will be sloshing around and causing fluctuation of the float level and associated resistance from the sender. Factory auto fuel gauges/indicators have some sort of buffering/filter/smoothing (not sure of the proper term) so the gauge doesn't bounce around while the tank sloshes. Is there any way to ad this to one one of the designs?
 
On most tanks I have seen the actual level sensor is encapsulated in a tube that inhibits the sloshing motion from screwing with the reading. That has been true of the trucks I have had anyway, can't vouch for a bike as it has been a long time.

What I would suggest doing is placing a voltmeter across the tank sensor and see what it does for a signal. Maybe rock the bike a little. Then I would worry about sampling and averaging only if I needed to.

Also, as I suggested to the last poster you may do better to open a new thread since this one as to original posting is pretty old.

Ron
 



I have almost the identical cct. as what you've shown here but I can't seem to find the right combination to get LED 10 (output pin 10 from the LM3914) to light up. I've tried several LED condinations.

Any ideas? I'm looking at 12 ohms to 132 ohms as well.

Thanks in advance.
 

browningbuck,

did you ever figure out the issue with getting LED on pin 10 to light?

Thanks. I have that issue right now. Everything else seems to work great.
 
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