10 LEDs lit it up acording to a potentiometer

[Killavolt]

Great thread!

I'm trying to put together a fuel level meter using a 10 LED bar and the LM3914 chip. My sender unit goes from 30 to 230 ohms. Can somebody run a sim and tell me what resistor(s) I will need to get the full range on the display with these values? It's automotive, so the voltage is 12 V or thereabouts. (It's fuel, it doesn't have to be exact! I just want to know when I'm running low)

Thanks.

 

[pkruger]

Great thread!
It's automotive, so the voltage is 12 V or thereabouts. (It's fuel, it doesn't have to be exact! I just want to know when I'm running low)

I want to do exactly the same Did you have any success yet?

Regards

 

[audioguru]

I don't want you to have a nice explosion, so I won't show you how.

 

[popicop]

Hi there, im new and seeking for a solution to MY circuit task ive made some tests with a LM3914N.

It is very simple to use a LM3914, since you will be using the cars power, fist try a votage regulator so you can have the same (lets say) 5 volts. The simplest array for this LM3914N will do just fine, you onley need to try some diferent value pots (mabe 10k to 100k). The real trick is how you are planing to make the gas level move the pot. Other wise its all done

 

[popicop]

By the way, ill post MY problem as soon as i check if some one has allready needed something similar

 

[Screech]

I think this circuit may work for that Fuel Meter thing.
Am I right audioguru/danielsmusic?
Is the Led brightness ok as R1 will be anywhere from 1030 - 1230 Ohms?

Adjust the RH Pot so all the leds light up when the fuel tank is full.
Adjust the RL Pot so all the leds turn off when the fuel tank is empty.


**broken link removed**

I didn't bother with drawing the other connections, as they are the same in all the other posted pic's.

P.S.
What does the ADJ pin do on the LM3914?
I don't understand it in the data sheet.

 

[audioguru]

Hi Screech,
Your circuit looks fine, except the ADJ pin resistors aren't shown.

The ADJ pin on an LM39xx is similar to the ADJ pin on an adjustable voltage regulator LM317. A two-resistors voltage divider from the OUT pin to ADJ then to GND adjusts the regulated reference voltage at OUT.

 

[Screech]

Thanks audioguru.

I think my 10k pots will be too hard to adjust in my above circuit. It's a case of hit/miss tuning.

Killavolt, I too have a fuel sender unit waiting to have a circuit built for it.
I think this below circuit is closely tuned for your sender.
**broken link removed**
I didn't bother with drawing the other connections, as they are the same in all the other posted pic's.

 

[djtaylor1]

Interesting thread. I was reading this because I have an LPG tank which I want to measure. Presently it has a 90R sender which is displayed via a 4 LED's which display Full, Empty and two reasonably indeterminate states in between!

For those mentioning explosions and how to move the pot, these concerns don't exist, the float and sender is already in the tank, we're just connecting up to the connections externally.

David.

 

[audioguru]

Maybe the sender is designed not to make a spark with a very low current through it so its voltage is very low. If you just connect 12V to it then you very well might have a nice big explosion!

 

[djtaylor1]

Maybe the sender is designed not to make a spark with a very low current through it so its voltage is very low. If you just connect 12V to it then you very well might have a nice big explosion!

In my case, no more so than creating a nice spark next to the tank as the sender gubbins is on the outside of the LPG tank, the sender float operates a rotary tube to the outside world and that's where the pot is.

David.

 

[audioguru]

First this thread talked about adding a bar graph display to a volume control.
Then somebody wanted to connect a bar graph to the sender in his car's gas tank.
Now you have a propane tank??? For my barbeque I have two tanks. When one gets empty then I use the other one.

 

[djtaylor1]

First this thread talked about adding a bar graph display to a volume control.
Then somebody wanted to connect a bar graph to the sender in his car's gas tank.
Now you have a propane tank??? For my barbeque I have two tanks. When one gets empty then I use the other one.

Sure, LPG fuel for the car, real gas instead of gas(oline)

Yes I can switch over back to petrol, actually it does it automatically when the LPG runs out but given the price differential it's not something that's desirable and we just use the odometer to gauge when to fill up but it has always been a long standing thought to provide better resolution. Most petrol senders are up to and around 300R, LPG senders are typically 90R. It's a common question in the LPG forums. I wouldn't mind interfacing it to the cars fuel gauge to display LPG level when on LPG and petrol when on petrol but that's another story altogether.

Diverse thread but common problem.

David.

 

[audioguru]

Is your car a taxi? Here, many taxis run on barbeque gas. They stink even more than a diesel.

 

[djtaylor1]

Is your car a taxi? Here, many taxis run on barbeque gas. They stink even more than a diesel.

No, plenty of cars run on LPG in Europe, the cost differential makes it attractive though it's not a mainstream fuel. Our exhaust just smells like when you open an oven door, a catalytic converter on petrol smells so much worse.

Besides, it's not the smell that should be your concern, it's the particulates in diesel exhaust and HC byproducts that will get you!

David.

 

[audioguru]

Why does gasoline cost so much in Europe? Here we get a little from the local sand up North and extracting it is expensive because it is in thick tar that needs heating. Most comes from Venesuela and the Middle East which are both very far away.
Our government takes a huge profit and still our price is 1/3rd of the cost in Europe.

Most stoves in Canada are electric since electricity is also pretty cheap here. Most houses are heated with natural gas that simply comes out of the ground.

 

[djtaylor1]

Tax, simple as that.

The government(s) have built a revenue model around the motorist and so while they talk about reducing emissions, if we all suddenly left our cars at home and walked, the economy would instantly collapse.

About 80% of the petrol cost in the UK is tax, it's about 5% on LPG.

David.

 

[audioguru]

Here in Canada, nearly everybody pays income tax (except me, I'm retired and collect a pension). Maybe in the UK hardly anybody pays the income tax as they should so the government taxes petrol instead. Then the petrol tax is not fair to people not making much money because it is not a percentage of their income. It is most of their income (like my income tax was?).

 

[djtaylor1]

Oh we pay income tax too as well as plenty of others and yes, the tax on petrol hits the poorest the most but still hits everyone. Anyway, this is pretty much waaaaay off topic now

 

[stratcat]

The LM3914 chip will do this. Also does single dot display.
HTH, Emory