Transistor Output Converter Help

raykur

Member
R
Join Date
Aug 2012
Location
Singapore
Posts
8
Hi All,

I have batch controller with a passive transistor output. This controller receives setpoint input from operator, when that setpoint is reach it will trigger the 24VDC solenoid valve.

Before the setpoint is reach, it gives 2VDC output and when it reaches the setpoint the voltage turns 0VDC.

I need somekind of converter to change this 2V transistor output to become 24V. Any advice will be much appreciated
 
Since we are a PLC forum, you could deploy a PLC with TTL input and relay output provisions.
The TTL input will detect the 2V transistor output as a "high" and the ladder logic could switch a relay output which would "pass" the 24V voltage.
 
Hi James,

What do you mean by a "compare circuit" do you have any drawing or reference I can look.

I was thinking to build a transistor with a 24V power supply.
 
Raykur - do you have a link for this controller? It sound like an open collector NPN output. It may be able to drive a small relay with the relay's contact driving the valve. The specifications of the controller's output will help to determine the best course.
 
Hi Damian,

So +24V to one leg solenoid valve

There is 2 output (+ and -) from the controller. You mean the (-) side to the other leg of the solenoid ?
 
It depends on the specific unit you have. There are different ones with the 'passive transistor' output. Look at the manual.

Tie one side (the + side if it is so marked) of your solenoid to the + side of the 24 VDC supply. Tie the other side (the - side if it is marked) of your solenoid to terminal 8.

If your controller is powered by the same 24VDC you are using for the solenoid then you are done.

If the 24 VDC for your solenoid is not the same as the power for the controller then also tie the - lead from the power supply to terminal 7.
 
raykur said:
when that setpoint is reach it will trigger the 24VDC solenoid valve.
Click to expand...
A batch controller typically turns the output OFF when the setpoint is reached.

Note the logic of the 2Vdc output
raykur said:
Before the setpoint is reach, it gives 2VDC output and when it reaches the setpoint the voltage turns 0VDC.
Click to expand...
The output is high until the total reaches the setpoint, then the output goes to zero.

This is probably what you are expecting but the terminology "trigger the solenoid" usually means turn the solenoid on. A batch controller keeps the solenoid on until the batch total is satisfied by reaching the setpoint.
 
Hi Bernie,

I try to use a NPN transistor to trigger the solenoid valve. It works good without the solenoid valve, my DMM is showing 24 volts and when the set point is reach DMM is showing 0 Volts.

But when connected to the solenoid, the voltage is 0 volts all the way. It seems that the solenoid is sucking the current. I am using a 24 volt 2A solenoid. Any advice on the transistor model ?
 
Check out the Io max output from the Fluidwell manual:

30rte11.jpg


Io max = 200mA

Your solenoid load = 2,000mA

Use the transistor output to drive a relay with a 24Vdc coil. Run the solenoid from the relay contacts.
 

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