# Thread: need help on making outflow valve gauge...

1. ## need help on making outflow valve gauge...

Hi
I am working on an RC circuit to drive a voltmeter.The concept of the circuit is that there is a three position switch in which if it is at the centre position, the voltmeter will be at 0.If the switch is pushed up,the voltmeter will increase gradually till it it at its maximum position, or if the switch is pushed back to the centre position, the needle will remain at the last position which it stops at.When the switch is pushed down, it the voltmeter will decrease till it reaches 0 or if the switch is pushed to the centre, the needle will also remain at the position it stops at.The voltmeter that i am using is a +5V.

Can anyone help me with this?probably with an explanation and a circuit diagram.

Also, is there a better way to come up with an outflow valve gauge?Any help with tis will be greatly appeciated. thks

Cheers

2. It sounds like you are asking for a guage that keeps track of peak flow as well as actual flow. Yes?

3. I think you need to give more details about what you are trying to do here.
For instance, the max value that you will see in the voltmeter... is this always the same value & if not, where is that voltage value coming from?

Another question would be what type of switch will you be using? SPDT, DPDT or other type or you don't care what type?

Are you hoping to accomplish this with just a switch, or would you consider having a logic circuit and/or other components as well? Doing that with just one switch would be a real challenge if not impossible I think (I have been known to be wrong on rare occasions

Once/if a circuit is available, how fast do you want the needle to reach maximum value in the voltmeter (gradually is not enough of an answer)?

I don't know if I or anybody can help you, but I do think they may also want to know the answer to these questions.

Maurice

4. After a bit more thought, I think you could do it with this circuit using only one SPDT switch:

Basically, the logic is this. When you flick the switch up, capacitor C1 will start charging via variable resistor R1 up to maximum voltage V. The voltmeter will show the votage in C1 & how fast the needle moves will depend on the values of C1 & R1 and you can change R1 to tweak the rate of change.

When you center the switch, C1 will retain the charge and the voltmeter will read the voltage value in C1. Eventually C1 would discharge slowly via the high resistance voltmeter, so you may want to add another high value resistor R3 to slow down the discharge even more.

When you flick the switch down, C1 would discharge via R2 and you can also control how fast it discharges if you use a variable resistor as shown.

In all cases, putting the switch back to center does not change the existing stable value in the voltmeter.

For the values of C1 & R1, here is a good reference that talks about time constants (R x C) so that the needle will rise at a suitable rate:
http://www.kpsec.freeuk.com/capacit.htm#timeconstant

Hope this helps but let me know if you have questions.

Maurice

5. Maurice. This is fantastic information. Thanks for adding your 2 cents worth.

Truly Outstanding.

Trev

6. Originally Posted by Trevor Hale

Trev
" 2 cents" ??? . I thought that was worth at least a buck

Maurice

7. Maurice,

Is this Ebay? I'll give you \$1.01?

Seriously... sweet circuit.

I am guessing her that the original poster is maybe working on simulating the cabin pressurization valves?

best,

.....................john

8. Originally Posted by JBaymore

I am guessing her that the original poster is maybe working on simulating the cabin pressurization valves?

best,

.....................john
I must confess I have no idea what good this circuit is as is. There has got to be more to it, otherwise it is just a dumb display of a rising or dropping voltage that has nothing to do with actual FS events.

Maurice

9. Yes,

I agree with you Mo. However the funny thing about it is, I need to do the same thing in my cockpit. I have 2 analog volt meters in my pit, that check (batt1, Batt2,APU,GEN1,GEN2,GEN3,HORIZ,IRS1,IRS2,IRS3) Battery voltages. Of course flightsim will show 7 segment readings of Battery voltages, however not analog readings, so I needed this circuit to my Power supply to appear for the eye candy.

I would give you to 2 bucks you request LOL

I purchased 2 cheap analog volt meters (actual multimeter's) and am going to rip the meter off and extend the cables. But if I had seen this in advance,m I would have used this method instead.

thanks buddy.

Trev

10. Trevor,

I have the analog voltmeter in my pit actually monitoring the various supply voltages that actually RUN the pit...... my 12V, 9V, 5V, and 3V supplys. So while "eye candy"...it has a real function and I watch it for REAL...... making sure all is well with the hardware.

I display the "in sim" voltage and and amperage on a Phidgets output display too.

best,

.................john

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