smoothing out voltage spikes and dips?

[scampo77]

Re: smoothing out voltage spikes and dips?

Sorry I didn't realize that there was a 3 wire divider in a float set up like this.

I had nothing before, this is a one off thing of left over parts

[budm]

Re: smoothing out voltage spikes and dips?

Most fuel senders are 2-pin variable resistor setup, never seen 3-pin type used in the car. 3-pin potentiometer type are used in most electronics such as you volume control on the radio.

[budm]

Re: smoothing out voltage spikes and dips?

Be carefull on what you see on internet.
Google 'Fuel gauge using LM3914'
Example:
http://www.electro-tech-online.com/e...ng-lm3914.html

Did the author actually built and tested what get posted?

[ben7]

Re: smoothing out voltage spikes and dips?

Be carefull on what you see on internet.
Google 'Fuel gauge using LM3914'
Example:
http://www.electro-tech-online.com/e...ng-lm3914.html

Did the author actually built and tested what get posted?

LOL, that was an epic design fail!

[ben7]

Re: smoothing out voltage spikes and dips?

This is the revised circuit.

1x LM3914
3x 1N4148 (D1-D3)
10x red/green/yellow (your choice) LEDs
2x 10uF 25v capacitor (C1-C2)
1x 100uF 16v capacitor (C3)
1x 2N3904 (Q1)

Optional - 1x 1A fuse

R1 - 1k
R2 - 4k7
R3 - 10k
R4 - 90 1/2watt
R5 - 10k
R6 - 10k
R7 - 2.2k

All resistors are 1/4watt unless specified.

The 9.35v connections connect to each other, and the Vref connections connect to each other too.

Also one important thing, does the float sensor read a higher resistance or lower resistance when all the way down? (when the tank is empty)

When we finish the design and you build the circuit, its a good idea to install a 1A fuse also, for good measure.

[budm]

Re: smoothing out voltage spikes and dips?

is this new diagram based on me keeping the Rsensor as a 0-100ohm float? and it is empty (one bulb lit up) at 5 ohm? and full (all 10 bulbs) at 85 ohm?

Hi Ben, 85 Ohms = full, 5 Ohms when empty if I read his post correctly.
By the way, most sensor assembly has one end attached to the tank which is ground the other end go to the Gauge on the dash with regulator circuits.

[scampo77]

Re: smoothing out voltage spikes and dips?

am i understanding this correctly?

please excuse my horrible horrible drawing (yes i am university educated)

[ben7]

Re: smoothing out voltage spikes and dips?

am i understanding this correctly?

please excuse my horrible horrible drawing (yes i am university educated)

You have the diodes backwards, and the 2N3904s pinout is EBC with the flat side facing you.

[scampo77]

Re: smoothing out voltage spikes and dips?

thanks ben i switched them around and it took off. i just wanted to make sure i had the collector leg integrated into the circuit correctly. if you look at the time i wrote the picture it was the middle of the night and i was half asleep and just threw something down on paper.

it is working! but in reverse. tank is empty, 0 ohm, 10 bulbs lit up and full 85+ ohm i have one light on.

and absolutly no damping of the pin 5 circuit. it is still reacting very much in real time. and i even have a .47uF in C3 spot

i am having trouble getting my fingers on a 90 ohm 1/2 watt resistor. wat happens if i ....

a) put in 100 ohm in R4?
b) put in a 82 ohm in R4?

[budm]

Re: smoothing out voltage spikes and dips?

BTW, I am still working on the diagram for you, just trying to simulate it on my computer.

[ben7]

Re: smoothing out voltage spikes and dips?

thanks ben i switched them around and it took off. i just wanted to make sure i had the collector leg integrated into the circuit correctly. if you look at the time i wrote the picture it was the middle of the night and i was half asleep and just threw something down on paper.

it is working! but in reverse. tank is empty, 0 ohm, 10 bulbs lit up and full 85+ ohm i have one light on.

and absolutly no damping of the pin 5 circuit. it is still reacting very much in real time. and i even have a .47uF in C3 spot

i am having trouble getting my fingers on a 90 ohm 1/2 watt resistor. wat happens if i ....

a) put in 100 ohm in R4?
b) put in a 82 ohm in R4?

You will need to connect Rlow pin of LM3914 to ground, and the Rhigh pin connects to the voltage divider made by R5 and R6. This means that D2 is not going to be used at all.

Try a 100uF or 470uF cap for C3.

[scampo77]

Re: smoothing out voltage spikes and dips?

ok i switched them now they just all come on and stay on. and my hi ref fluctuates from 2v to 2.2v

[ben7]

Re: smoothing out voltage spikes and dips?

ok i switched them now they just all come on and stay on. and my hi ref fluctuates from 2v to 2.2v

Does your circuit look like this now?

(I did add D2 back in. Its in a different place now. Also the float sensor and the R5-R6 voltage divider has been connected to the Rhigh pin instead of the Rlow pin. see if it changes anything)

[budm]

Re: smoothing out voltage spikes and dips?

OK, this is REV1 for what I come up with, based on calculation with sensor 5 Ohms min (Empty tank, no LED ON) and 85 Ohms Max (full tank, LED#10 ON).
I left out the damping circuits for now to see how well the range of the sensor is.
The calibration is done by setting the sensor to full resistance then adjust VR1 till LED #10 is ON.
To make LED1 to be on at empty will be a little more complicate due to the voltage windows (sensor @max and sensor @min).
Notes: you will have to find out which end of the sensor is tied to the chassis ground.

[ben7]

Re: smoothing out voltage spikes and dips?

OK, this is REV1 for what I come up with, based on calculation with sensor 5 Ohms min (Empty tank, no LED ON) and 85 Ohms Max (full tank, LED#10 ON).
I left out the damping circuits for now to see how well the range of the sensor is.
The calibration is done by setting the sensor to full resistance then adjust VR1 till LED #10 is ON.
To make LED1 to be on will be a little more complicate due to the voltage windows (sensor @max and sensor @min).
Notes: you will have to find out which end of the sensor is tied to the chassis ground.

Good job!

[budm]

Re: smoothing out voltage spikes and dips?

Thanks, tt is only good when it does what he wants to do, then I will make inprovement from there, crossing my fingers.

[ben7]

Re: smoothing out voltage spikes and dips?

I was using the diodes D2 and D3 along with R3 and C3 to make a time delay. D3 prevents the capacitor from draining through the float sensor pot.

lol, is this becoming a competition to see who could make the best circuit?

EDIT: Did you get the 5-85 ohm pot idea here? Because I think he was just asking. He should measure the resistance of it when full and empty. That would help a lot

[budm]

Re: smoothing out voltage spikes and dips?

I have a feeling he did not hook up your circuit like you have shown in the drawing.
I try to make the circuits as simple as possible. I hope he can try mine also.

[budm]

Re: smoothing out voltage spikes and dips?

Please disregard the diagram of REV 1, I drawn the connection wrong on the Ref adjust and Refout pin connection.
Here is the REV2 with the correction.
Hi Ben:
Yes,I hope the 5 Ohms-85 Ohms range is the correct info.
By the way how did you do the link like that with the word here and it links to the URL.

[tom66]

Re: smoothing out voltage spikes and dips?

If this is an automotive system, I'd *highly* suggest an TVS (e.g. 1.5KE) and fuse (auto 1A if possible will be more than enough.)