Pressure Sensor circuit help

[richacm]

Why not do as I do, and get FREE SAMPLES from Freescale, OnSemi etc etc etc...
Sometimes you'll need to pay the shipping, but the value of the freebies far outweighs any postage costs!
I've built a barometric altimeter, good to 50K feet, and has 1 foot resolution using these samples.. No op amps required!!

Wow, they are pretty cool aren't they. Thanks for the info - I may use them in the future from some other ideas. At the moment I am enjoying playing around with what I am doing as I am learning stacks and progressing well.

Once I have it all completed and working I'll take photo's and post a completed cicruit.

 

[ericgibbs]

That would be fantastic thanks. Been looking at the applications in the 7805 datasheet and couldn't figure out one that would suit.

Hi,
Added a 7805 Vreg to your circuit, also some decoupling caps.

The heat sink on the 7805 may not be required, depends upon the current load of your project.

EDIT: the 20mA current per LED calculation needs checking,, I = [Vpin-Vled]/Rs .

 

[Ubergeek63]

Sorry about that...I should. I need a 0-5psi pressure sensor. Need to measure 3m depth of water which is around 4.27psi.

That's interesting about the digi key site. I was using my local NZ site which is normally not too bad but I think they may be restrictive in their products available which affects the price.

They are probably only deal in industrial transducers....

In case you did not go and do the search at digikey:

Digi-Key - MPX4080D-ND (Freescale Semiconductor - MPX4080D)

is an amplified 0-5V out with 0-11PSI in for $15

 

[richacm]

Went to the digi key site and choose a few components I wanted. When I went to checkout they said the shipping to NZ was over $80! Even rang them up and asked why it was so expensive, they just said it was the standard cost of shipping internationally....pitty cause other sites do it for under $10. I will hunt around for equivalent parts elsewhere.

Thanks for looking that up for me.

 

[richacm]

Hi,
Added a 7805 Vreg to your circuit, also some decoupling caps.

The heat sink on the 7805 may not be required, depends upon the current load of your project.

EDIT: the 20mA current per LED calculation needs checking,, I = [Vpin-Vled]/Rs .

That is absolutely fantastic....couldn't ask for anything better. I much appreciate the work involved. If you weren't the other side of world I would offer to buy you a beer

 

[Ubergeek63]

Went to the digi key site and choose a few components I wanted. When I went to checkout they said the shipping to NZ was over $80! Even rang them up and asked why it was so expensive, they just said it was the standard cost of shipping internationally....pitty cause other sites do it for under $10. I will hunt around for equivalent parts elsewhere.

Thanks for looking that up for me.

Not a problem. If you look around you should be able to find distribution locally.

Distributor Network

for their NZ distributors.

 

[richacm]

I have updated the circuit with all your replies.

I have included the 7805 like you described and I also placed in 2 ULN2003 components to drive the LED's. Did my calculations based on a 5V supply to the LED's. If it was a 12V supply then the Resistor value would be 450hm:.

I've also thrown another spanner in the works as I forgot to mention that the LED's will be about 4-5 meters away from the components. I have therefore placed a capacitor on the 5V supply. Is this all I need to do? For long distances does it matter whether 5V or 12V are transmitted on the wires?

Cheers,

Craig

 

[ericgibbs]

Morning Rich,
Check the voltage supply to the anodes of the LED's, where is it.??
Whats the [LED] 100uF going to do, wired in that way..

 

[richacm]

I thought that...I just saw it on a diagram somewhere during my searches. If I place it in parallel will that take care of the long wire?

 

[ericgibbs]

I thought that...I just saw it on a diagram somewhere during my searches. If I place it in parallel will that take care of the long wire?

hi,
Look at the modified drawing.

 

[richacm]

Got it - thanks.

 

[MohammedPUD]

Hi.
You always need to install a negative feedback "Variable resistance" so you can adjust the output signal the way you want it.