Self Powered Remote Sensor

[Geoff White]

We have a customer that wants to have a portable level sensor that can be moved between tanks and signal when the tank has dropped below a level.

To do this the sensor (probably a capacitive sensor clamped to a level tube) would need to be connected to a box that is providing both power for the sensor and wireless comms.

The remote box would need to be rechargeable.

I know there a numerous ways this could be built from various IOT boards but is there some real product in this niche?

[damica1]

http://www.tanksentinel.com/

[OkiePC]

We have a sample on the shelf from Digi that sounds close to what you might need:

https://www.digi.com/products/networ...connect-sensor

We have not field tested it yet.

[Geoff White]

Thanks guys.

The customer is a tightarse and wants a single portable sensor because they only use one tank at a time and have heaps of them. The tanks are in close proximity so cellular data is not needed.

The Digi looks nice but it uses non rechargable batteries that only last 2 years at 2 samples per day!

[danw]

A typical 4-20mA transmitter will run for several days continuously on a triple 9V transistor battery (3 batteries wired in series) pack.

Banner node radios operate on a lithium D cell for a couple years and can be turned off with the faceplate pushbutton.

Find the correct type of 2 wire loop powered level transmitter (pressure, ultrasonic, radar, whatever), power that with relatively cheap 9V batteries that are easily replaced and a Banner node radio and gateway radio. Gateway radio is near whatever you're sending the level signal to and is 24Vdc powered.

[OkiePC]

Originally Posted by danw

A typical 4-20mA transmitter will run for several days continuously on a triple 9V transistor battery (3 batteries wired in series) pack.

Banner node radios operate on a lithium D cell for a couple years and can be turned off with the faceplate pushbutton.

Find the correct type of 2 wire loop powered level transmitter (pressure, ultrasonic, radar, whatever), power that with relatively cheap 9V batteries that are easily replaced and a Banner node radio and gateway radio. Gateway radio is near whatever you're sending the level signal to and is 24Vdc powered.

That reminds me of a little tester I had that I got from a Banner rep. It was a small box with spring terminals and a DC micro plug and a couple of LEDs. You could plug in a photocell or prox switch and test it by looking at the LEDs. It ran off 3 9V batteries. I think they were available for sale and might make a good basis for the OP to build something.

https://www.alliedelec.com/product/b...dbq5/70168288/

[OkiePC]

Another place to look:
https://www.onsetcomp.com/products/data-loggers/zw-008
https://www.onsetcomp.com/products/d...ggers/ux90-004

We used Hobo Loggers for temporary temperature monitoring at a food plant where I used to work. They are surprisingly robust and easy to use and relatively economical. We stuck them inside freezers as low as -40F. Ours were not the wireless type, we had to retrieve them and upload the data. Their tech support was good too, so you might call them with your application and see what they recommend.

[chud]

https://www.youtube.com/watch?v=NGRqX5sJZ0U

[diat150]

check out signalfire or oleumtech. but neither is really cheap.

[James Mcquade]

this maybe a stupid question, but how will the customer be able to tell
one tank level from another?

james

[Dirt]

Originally Posted by Geoff White

The customer is a tightarse and wants a single portable sensor because they only use one tank at a time and have heaps of them.

Made me wonder, who is moving around the sensor for free?

[seth350]

If you are keen on the idea of building your own.

An Arduino with analog in, a 4-20mA level sensor (an ultrasonic sensor from Automation Direct), and a rechargeable battery could help your frugal friend. Then you could pull the data off the Arduino using WiFi over ModbusTCP.
You may even be able to mount the Arduino and battery on top of the level sensor in a small plastic box.

Battery life should be OK but read rates and sensor selection will determine battery life.

[Geoff White]

Originally Posted by Dirt

Made me wonder, who is moving around the sensor for free?

The sight lines are a tube running up the side of the tank. The sensor would only need to be clipped to tube at arms reach from the bottom of the tank.

It's not a stupid idea, just half arsed.

[OkiePC]

So you really just need a single discrete input? Or is it going to be analog?

[Geoff White]

Just a single digital input (probably a capacitve prox)