Controlling an external solenoid valve Agilent 7890 GC

[sllimbri65]

I need to know how I can turn an external solenoid valve on or off by using the valve options and runtime events programming. i have seen other posts from several years back but nothing recently. I wish to use a 24v/3W solenoid.

I cut the following info from a previous post by GASMAN...
You need the connector P22, which I believe is marked on the board.

For Valve 1 use pins 5 and 13
For Valve 2 use pins 6 and 14
For Valve 3 use pins 7 and 15
For Valve 4 use pins 8 and 16

So I set my GC configuration for valve 4 and set the runtime events to toggle this valve on and off during a run. I was measuring the volts with my VOM. It never turned off. The volts were a constant 28v. What am I doing wrong? Am I missing something here?

[Johnny Rod]

I havne't dabbled with this but the manual says about exterrnal valve control:

Valves 5 and 6 can control a low-power external device, 24V DC up to 100mA.

pins you need are pin 1 for valve 5, pin 2 for valve 6, and pins 3 or 4 for ground to complete the circuit(s), on the External Event connector on the back of the GC. This is one of the sockets that looks like a PS/2 mouse connection. The pin configurations are on page 365 of the 7890 advanced user guide (download this from the Agilent website, about 6MB). You can buy cable G1530-60590 or you could make something suitable.

for valves 1-4 they are good for up to 24V DC/13 watts but the wiring is located under the right side cover of the GC (connectors V1-V4), I think the idea is you plug in the pneumatic valve via the Agilent wiring harness.

[sllimbri65]

Thanks, I read the manual but I think I need the internal valve connectors for valves 1-4 and the manual is lacking in much info there. I was hoping someone with direct experience with this could respond.

[Johnny Rod]

The pin numbers from Gasman are right for a 6890, I would also think they are right for a 7890 but I can't find any info, except that Vici quote the same part number for both:
http://www.vici.com/act/mic.php
Why don't you just use it as valve 5 or 6?

[sllimbri65]

I can't figure out how they work. If I measure the volts between pin 4 and 1, it never varies from 28 volts. Even when the event table is set to off. Why is this and how would I use it to turn a 24v/3W solenoid on/off?

[Johnny Rod]

Frankly, no idea, are you sure you have the correct pins? Or if you have the appropriate event cable, the wires are colour-coded. Are the valves set up in the instrument configuration?

[sllimbri65]

I don't have a cable. I was just sticking small wires in the holes and measuring with a vom. The valves are configured.

[Gaston]

I know it's probably not kosher to revive such old threads, but I'm currently having the exact same issue with a 6890N. I want to control a solenoid valve using the 24 VDC external event output from the GC. From the information in the manual (this), I should use pin 1 (which is valve 5) and that pin 3 as the ground, although I am not completely sure this is the correct wiring for my solenoid valve (i.e. it has two terminals + ground). In any case, the multimeter always shows 26 V between pins 1 and 3, independently of whether valve 5 is on or off in the GC keyboard.

Does anyone have more info on how to solve this? Any tips would be greatly appreciated!

[GasMan]

My original posting I believe was for a 5890, and for the connector on the main board. You have the correct manual, and the pins that you mention should work. Just make sure that your solenoid valve does not need more than 75mA, otherwise the power supply will shut down. You mention that your solenoid has three terminals. I would check the resistance between the two terminals not marked 'ground', and should be more than 320 ohms.

I seem to remember that there were some 6890's where they switched the ground contact, so you always measured 24 volts on the 'hot' contact.

Gasman

[Gaston]

Thanks, GasMan. The resistance between terminals 1 and 2 in the solenoid valve is about 50 ohm. The bag has this about the wiring:



Anyhow, I'm super stumped about the pins. The 24 VDC output pins (1 and 2) always have 26 V, no matter what I do with the valve configuration in the GC. I'm thinking this GC is malfunctioning, or I am doing a very basic mistake which I cannot see

[Gaston]

Dear GasMan,

I looked into some old threads, and here you mention that there will always be 24 V on the solenoid using the external valve controller. That means I probably chose the wrong solenoid valve (I got an NO instead of an NC), but I still don't understand why switching the valve "position" on the GC keyboard does not change the voltage at all.

[Peter Apps]

Hi Gaston

If the post that you found is mine, then it is truly a golden oldy ! That post is 8 years old ! I can only suggest that you do what I did; plug the solenoid into the connectors and see if it switches. The valve will take the 24V, so the worse that can happen is that nothing happens. You can get around the N/O N/C problem by reversing the open - close commands (although this might mean that the valve is energized for longer than it otherwise would be.

Peter

[Gaston]

Hi Peter,

Yeah, that was your post. An oldie but a goodie

I did what you mentioned, but unfortunately, nothing happened. To be more specific, I did the following:

(1) Connected pin 1 (of the external events output) to terminal 1 of the solenoid valve, and pin 3 to the ground terminal of the valve. Nothing happened. Turned Valve 5 ON in the GC keyboard. Nothing happened.

(2) Pin 1 to terminal 1, and pin 3 to terminal 3 of the valve. Nothing happened with Valve 5 turned on or off.

Peter, you connected your solenoid valve to the internal valve drivers? (1-4). My solenoid valve draws 8 W at 24 VDC. Maybe that's the problem?

[Gaston]

Well, 75 mA x 24 V = 1.8 W = no way I'm operating that valve with the external valve driver

[thepsa]

Hi Gastón,

have you checked the power consumption of your valve? If the power requirement of the valve magnet is too high, it won't open. The GC connection might not give you more than 2 W.

Regards,
PSA