Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
hi bb,
Reply to your results. Please confirm what type of OPA you are now using.
#1.
Measuring VS, I can also get 0.07v to 0.77v and beyond (200 Ohm pot) from Full to empty tank.
; The reading should be as you have posted ie: 70mV thru 770mV
#2 Measuring the voltages on vo1, it reads (from full tank to empty) 0.63v to 3.1v and beyond but I can't get below 0.63v.
You should be able to get down to vo1 = +0.35v
;
Note that I can go beyond 3.1v (Since I'm using a 200 Ohm trimpot to emulate the sender) but not below 0.63v (0 resistance already). The vo1 = +3.1v is what I would expect.
Note: some pots have 'end' resistance and not go down to a 'complete zero R'
#3 Measuring the voltages on vo2, it reads (from full tank to empty) 2.40v to 0.64v but I can't get below 0.64v. The +0.64v minimum is making the LM3914 to light LED's #1 and 2
The above measurements were taken at the standard SPAN and ZERO pot settings (14.5K and 19K).
Increasing the ZERO pot's resistance will light the 2 upper LEDs (Making it an 8 functioning LEDs), but can't get to turn off the 2 lower LEDs even by tweaking both trim pots. This is what I would expect the ZERO pot to do.
As a result, Only 6 LEDs are functioning on the full fuel sender range. The last 2 LEDs stays on forever, while the upper 2 leds don't light forever the (0.64v to 2.40v range) at the standard pot settings. This error is due to the +0.64v offset error.
If the OPA is causing these problems , there is a solution, adding a resistor to the LM3914, I will explain how to do that, if required.
I'm using another LM358 that I just bought this morning. Measuring every resistor doesn't give accurate readings like 470R rates at only 457 Ohms etc... will these affect vo1? Almost every resistor doesn't give exact readings.
How about if we'll just make the LM3914 minimum to 0.64v? Even if i connect VS to the ground the minimum of vo1 is still 0.64v lighting the last 2 LEDs.
OK,
I will post a value for a resistor on pin# 4 on the LM3914, so that you can adjust off that 0.64V
EDIT:
hi,
Wire up the LM3914 as shown in this image, the 5K pot will enable you to back off the +0.64v at the EMPTY tank end. LED#1.
I have built the tank sensor using LM358 and it works perfectly OK.??
I cannot say at this time why your version is not working as expected.
Just to clear things up. All 3 pins of the trimpot will be used this time right?
Leg #1 connected to ground.
Leg #2 (wiper) on pin #4 of LM3914.
Leg #3 on pin #6 of LM3914.
Is this correct?
The LM358 I bought were cheap chinese replica of the original National and Fairchild versions as they are the only ones available. So I don't expect them to be of accurate specs.
Just to clear things up. All 3 pins of the trimpot will be used this time right?
Leg #1 connected to ground.
Leg #2 (wiper) on pin #4 of LM3914.
Leg #3 on pin #6 of LM3914.
Is this correct?
The LM358 I bought were cheap chinese replica of the original National and Fairchild versions as they are the only ones available. So I don't expect them to be of accurate specs.
Everything's working perfectly now. Its now even attached to my motorcycle... really looks good and functions awesomely! Thank you so much. I'll be observing the project for a few days if anything weird might happen. Fuel sloshing will be observed also.
Next: Digital Speedometer on a PIC16f84a with 3 multiplexed 7-segment displays. I will be needing your help on how to tweak a bicycle speed sensor (from a broken cateye, magnet type sensor) to convert its output that is acceptable and countable by the MCU.
Everything's working perfectly now. Its now even attached to my motorcycle... really looks good and functions awesomely! Thank you so much. I'll be observing the project for a few days if anything weird might happen. Fuel sloshing will be observed also.
Next: Digital Speedometer on a PIC16f84a with 3 multiplexed 7-segment displays. I will be needing your help on how to tweak a bicycle speed sensor (from a broken cateye, magnet type sensor) to convert its output that is acceptable and countable by the MCU.
Our fuel gauge is still working fine, thou fuel sloshing is very annoying. I have bought 1uF non-polar capacitors (remember the 1uF we discarded?), will these alleviate the problem? Or we need a major modification to average the fuel readings?
Wow never thought it would be that easy to modulate sloshing. Thou I won't be able to try it till tomorrow since its already 11PM. I'll let you know tomorrow. Goodnight!
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
