Education Electronic Circuit Help

When you get it finished stick a few pics up, be interesting to see

 

Will do! Also working on an Arduino build which should come to life on Wednesday!

 

+ -| water |- -
water
water
+ -| water |- -
water
water
+ -| water |- -

 

Ok so I have updated the circuit slightly I need to move on to the relay circuit for the LED's.



If I am right the AND gate chip will output a maximum 12V at 3.6mA on each AND circuit. Chip link is here.

Can I use this relay?

 

Bear in mind that AND gate package has triple inputs. You'll need to connect a logic `1` (12V) to the unused input.

Couldn't you use a transistor rather than a relay for driving the LEDs?

 

Discontinued product

 

Waaaa! Ok I think it is time to find a decent circuit that the AND gate can trigger....

 

Are you not using LEDs to signal the water levels?

 

Ja but the AND gate only outputs 12V 3.6mA or am I reading that wrong?

 

Going to this family datasheet:
http://www.nxp.com/documents/other/HCT_USER_GUIDE.pdf

Your device is a HE4000B family, on table 1 you see metal gate CMOS 4000 HE output drive.

It looks like the standard output is 0.8mA @5V.

edit: Consider putting the 2 sides of the sensor at the same level:



edit2: You can replace the relays with cheap 2n2222 transistors or something simpler.

 

Ah yes! Having the sensors at the same level would make much more sense! So it can take 12V in and output 5V?

 

Do you want one led active at a time or can it have several LEDs lit?

 

I want to have them each light up in turn so when the tank is full there will be 3 LED's illuminated. I might have time to add a speaker with the last LED but I just need to get this bit sorted.

Thanks again for all your help!

 

Does your project require you to use AND gates?

 

No but it cannot include a programmed chip such as a PIC chip.

 

This is the AND gate chip I have selected: http://uk.rs-online.com/web/p/gates/0787476/

 

You could make it simpler by forgoing the AND gates and thinking of different connections between the opamps.

 

This is true but I quite like the AND gates, not sure why!

So... the AND gate is going to output 0.8mA at 5V. So I can just use that to power something like this? http://uk.rs-online.com/web/p/visible-led/2285483/ Although I would think the current is actually far too low.

 

Use 3 simple transistors to drive the LEDs.

 

Will look into that tomorrow night, bed time now. Thanks again for all your help, wish I could do something for you!