How do I get my Sensor Switch transistors

Thread Starter

RodneyB

Joined Apr 28, 2012
697
The post below was the original with incorrect information. the out put is from 0 to 3V3 so I would like to have an out put at 1,2 and 3 volts.

I have a sensor that has a range from 0 - 20mA.

I would like it to switch on something at every 5mA (4,10,15,20mA's) So I could in turn switch on something Larger. Like switch on a transistor that in turn switches on a relay.

Please can I have some guidance as where to start.
 
Last edited:

cmartinez

Joined Jan 17, 2007
8,218
I have a sensor that has a range from 0 - 20mA.

I would like it to switch on something at every 5mA (4,10,15,20mA's) So I could in turn switch on something Larger. Like switch on a transistor that in turn switches on a relay.

Please can I have some guidance as where to start.
I'd first convert its current output into a voltage output, then I'd connect its output to comparators to digitize the signal, and then switch whatever you want to switch using the comparators outputs...
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
I'd first convert its current output into a voltage output, then I'd connect its output to comparators to digitize the signal, and then switch whatever you want to switch using the comparators outputs...
Thank you

I will look at the sensor Data sheet and take it from there
 

cmartinez

Joined Jan 17, 2007
8,218
Thank you I will look for the components and then try to build it. I would have to build 4 of each of the circuits to switch at the required voltage if my understanding is correct
No... you only need to build one circuit as shown in the application note, then you use its 0-5V output and add four comparators to it.
Using a comparator is rather easy, but do you need assistance with that too?
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
No... you only need to build one circuit as shown in the application note, then you use its 0-5V output and add four comparators to it.
Using a comparator is rather easy, but do you need assistance with that too?
Thank you for your help, I made a mistake on the reading. Its 0 - 3V3 with a 5mA power consumption. I am going to edit my orginal post
 

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cmartinez

Joined Jan 17, 2007
8,218
Thank you for your help, I made a mistake on the reading. Its 0 - 3V3 with a 5mA power consumption. I am going to edit my orginal post
Well then, that simplifies things a lot. You no longer need the circuit in the application note, just the four comparators. How are you going to power your device?
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
Well then, that simplifies things a lot. You no longer need the circuit in the application note, just the four comparators. How are you going to power your device?
I am going to have a 12volt battery. I will use a 7805 to power the sensor. is there a single IC with four comparator
 

bertus

Joined Apr 5, 2008
22,270
Hello,

Do you have a datasheet of the sensor to post?
With the information, we can provide better solutions.

Bertus
 

cmartinez

Joined Jan 17, 2007
8,218
I am going to have a 12volt battery. I will use a 7805 to power the sensor
Then you have to think about battery usage, and overall efficiency. I do not recommend you use the 7805, but rather a small smps like these ones, that has a much higher efficiency.
Hello,

Do you have a datasheet of the sensor to post?
With the information, we can provide better solutions.

Bertus
Bertus, he posted the DS in post #9
 

Thread Starter

RodneyB

Joined Apr 28, 2012
697
I can use a power adapter. I chose a 12 volt battery 7Ah as I had successful with the help of this forum made a 12volt charger for this battery
 

cmartinez

Joined Jan 17, 2007
8,218
I can use a power adapter. I chose a 12 volt battery 7Ah as I had successful with the help of this forum made a 12volt charger for this battery
It's far better if you use a power adapter, since I'm under the impression that you intend to use your device continuously. Also, efficiency would cease to be a concern and the design would be far simpler.
Question #2, how do you intend to mount the components? Can you make your own PCB's?
 
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