# Pinch Valves Control

#### Zooz

Joined Nov 24, 2015
7
Hello,
I'm trying to control solenoid operated pinch valves through a computer. The valves I'm using are from Cole Parmer:
http://www.coleparmer.com/catalog/product_view.asp?sku=9830206

The Control of the solenoid pinch valves is using digital output pins from a DAQ card. The digital output should be directly connected to the TTL input of the valves. The valve should open when the digital output is set high (5V) and close when the digital output is set low (0V). Since the valves I'm using are not TTL, I will need to use a TTL switch with the valves. I'm thinking of using this switch from Texas Instruments:
http://www.ti.com/product/CD74HCT4316/technicaldocuments
I'm confused about the switch part and the control. I hope you guys can help.

#### AnalogKid

Joined Aug 1, 2013
8,487
The valve you selected runs on 12 VDC, and needs 333 mA of current to operate (4W / 12V = .33A). This is way too much current for an analog switch. It has "switch" right there in the title, but it is designed to switch low level signals like audio, video, and control signals, not power signals.

The required power switch circuit is not difficult or complex, but you can make it even easier if you can reverse the control polarity to close the valve with a high output. If you can, then to drive that with a TTL signal you will need a small power darlington transistor, a resistor, and a diode. Many small signal transistors are rated for 500-600 mA, but for something like this I think a fatter, more industrial-strength part is better. With overkill comes reliability. Another option is a small logic-level power MOSFET, but again I've found bipolar transistors to be more reliable in industrial applications.

If you can't invert your logic signal then a small signal transistor will have to be added to the circuit as an inverter. My schematic system is down, but I'll see if I can sketch something later. What is your skill set regarding designing a circuit, soldering parts, etc? Is this to go on a pc board?

Now that I've said all of that, another option is a small solid state relay. These would act like the small power transistor described above, (still need 1 resistor and 1 diode), but can be connected with the logic polarity you want without an intermediate inverter.

http://www.ixysic.com/home/pdfs.nsf/www/LCA701.pdf/$file/LCA701.pdf http://www.ixysic.com/home/pdfs.nsf/www/CPC1906.pdf/$file/CPC1906.pdf

ak

#### Zooz

Joined Nov 24, 2015
7
I will use two of the valves I specified in a bioreactor. I don't think the logic signals matter, the most important thing for me is that I will be able to control the valves (open/close). The control signal is a 0-5 Vdc TTL signal (ON/OFF). The control signal is used to regulate the power input to the valves, which opens and closes the valves. I think LabView and DAQ card can be used as a function generator, which provides a controllable 0-5V TTL signal. I was looking for TTL valves from the beginning but I couldn't find any! I know that the valves I found are the best to use, and for the TTL part I will need the switch I specified. The thing I'm confused about is how can I use the valves with the switch to do the job.

unfortunately, I'm not an expert when it comes to circuits. I've done soldering parts before. If you can help me with a sketch that would be very helpful.
Thank you so much

#### Zooz

Joined Nov 24, 2015
7
The valve you selected runs on 12 VDC, and needs 333 mA of current to operate (4W / 12V = .33A). This is way too much current for an analog switch. It has "switch" right there in the title, but it is designed to switch low level signals like audio, video, and control signals, not power signals.

The required power switch circuit is not difficult or complex, but you can make it even easier if you can reverse the control polarity to close the valve with a high output. If you can, then to drive that with a TTL signal you will need a small power darlington transistor, a resistor, and a diode. Many small signal transistors are rated for 500-600 mA, but for something like this I think a fatter, more industrial-strength part is better. With overkill comes reliability. Another option is a small logic-level power MOSFET, but again I've found bipolar transistors to be more reliable in industrial applications.

If you can't invert your logic signal then a small signal transistor will have to be added to the circuit as an inverter. My schematic system is down, but I'll see if I can sketch something later. What is your skill set regarding designing a circuit, soldering parts, etc? Is this to go on a pc board?

Now that I've said all of that, another option is a small solid state relay. These would act like the small power transistor described above, (still need 1 resistor and 1 diode), but can be connected with the logic polarity you want without an intermediate inverter.

http://www.ixysic.com/home/pdfs.nsf/www/LCA701.pdf/$file/LCA701.pdf http://www.ixysic.com/home/pdfs.nsf/www/CPC1906.pdf/$file/CPC1906.pdf

ak

I will use two of the valves I specified in a bioreactor. I don't think the logic signals matter, the most important thing for me is that I will be able to control the valves (open/close). The control signal is a 0-5 Vdc TTL signal (ON/OFF). The control signal is used to regulate the power input to the valves, which opens and closes the valves. I think LabView and DAQ card can be used as a function generator, which provides a controllable 0-5V TTL signal. I was looking for TTL valves from the beginning but I couldn't find any! I know that the valves I found are the best to use, and for the TTL part I will need the switch I specified. The thing I'm confused about is how can I use the valves with the switch to do the job.

unfortunately, I'm not an expert when it comes to circuits. I've done soldering parts before. If you can help me with a sketch that would be very helpful.
Thank you so much

#### AnalogKid

Joined Aug 1, 2013
8,487
You need to dig through the DAQ card specs and tell us the max output current the board can source at 5 V, and the max current it can sink at 0 V. Something to know is that TTL is a logic signal standard. The original TTL parts ran on 5 V and a TTL output coud sink 16 mA in the low state. BUT - TTL has come to mean a set of voltage levels, possibly without the current capabilities of actual TTL parts. So your DAQ card might be able to make TTL low compatible signal levels but not sink 16 mA, or sink enough current to energize a solid state relay.

ak

#### Zooz

Joined Nov 24, 2015
7
You need to dig through the DAQ card specs and tell us the max output current the board can source at 5 V, and the max current it can sink at 0 V. Something to know is that TTL is a logic signal standard. The original TTL parts ran on 5 V and a TTL output coud sink 16 mA in the low state. BUT - TTL has come to mean a set of voltage levels, possibly without the current capabilities of actual TTL parts. So your DAQ card might be able to make TTL low compatible signal levels but not sink 16 mA, or sink enough current to energize a solid state relay.

ak
Thank you for your help. I need the switch to make the input of the valves TTL. So the control signal is TTL meaning that the valves will open/close according to the digital out pin 0/5V. Unfortunately, I couldn't find TTL valves, so I decided to use the valves from Cole-Parmer along with a TTL switch. I'm still not sure if I can use that switch from National Instruments. I hope you can help with that.

#### Alec_t

Joined Sep 17, 2013
11,388
I need the switch to make the input of the valves TTL
The valves don't have a TTL input. They require just a 12V power source. In post #2, AK outlines the interface circuit you need, involving a Darlington transistor driver for the valve.