Resistors for volume sensos

[swanwick]

I have purchased one of @BrunDog volume sensors. Per his warning, it puts out 5v and the Uniflex input wants max 3.3v. So, I need a little volt divider circuit that will include a 1kohm resistor and a 2kohm resistor. Apparently these things come in 1/4 watt, 1/2 watt, 1 watt versions. Anyone know which of those I am going to need?

Also, Pete's web page does not indicate the wiring for the volume sensor. Does anyone have one of these? Is it power in, variable voltage out (the volume indicator), and ground? If so, what power does it need? I have an external 24v power source that I am using to power a proportional automatic ball valve. Can I also direct that to the pressure sensor?

Sorry if some of these questions are non-sensical. I am pretty novice with circuits.

 

[staffordj]

Resistor size does not matter, it should be very low power. You may want 1% accuracy resistors. Power is 12-30V, so your 24V ps will work well. Wiring is red to 24v, yellow to DC ground and blue to your voltage divider and then analog pin.

 

[swanwick]

Thanks @staffordj I am sending my 24v PS through a terminal block that goes to pins 2, 3, and 14 on the uniflex v2 and also to the proportional valve. Is it OK to have another slot in that terminal block going to the pressure sensor? OK to be splitting the power source among all these things? What if I get another volume sensor for the BK? OK to add that to same power source too?

I would think that proportional ball valve will use practically zero power, but the volume sensors will be always on.

Diagram attached (warning is not a proper electrical diagram). Also, does not yet show volume sensor.

 

[staffordj]

Yes it is ok to run multiple devices off a single power supply, you just need to check the power rating on you power supply. you should be able to get current or power useage from a device data sheet. In general, sensors use very little power, motors and heaters use more. Always on does not really matter, what matters is not exceeding the power supply capacity at one time. Ball valves have a small motor, so they will use more power than most sensors, but for a short time.

 

[AlexKay]

it’s usually not a great idea to use a voltage divider to power a device. Use a 3.3 V voltage regulator instead, like this one.

 

[AlexKay]

Oh, nvm, wasn’t reading carefully. If you just want to scale a signal, a voltage divider is just fine. 1/4 W resistors are overkill; you’ll be fine.

 

[day_trippr]

1/8 watt axials are about as small as one typically wants to have to handle and are well suited for signal conditioning like this...

Cheers!

 

[swanwick]

are 1watt ones ok for this application?

 

[BrunDog]

Not needed. Get 1/4 W. Very accessible from Amazon, etc.

 

[day_trippr]

Yeah, jeeze, 1W composite resistors would be huge.
I think even Hellen Keller could solder those in place, using a charcoal fire...

Cheers!

 

[swanwick]

Gotcha. Looks like I ordered 1/2w. Ordered another set of 1/4w and will return the 1/2's. Beauty of Amazon.

Thanks for the help. Will have the divider circuit ready for when the volume sensor gets here.