i’m new here, i hope this is the right place to ask this question:
So currently i am trying to setup an external air assist with a 24V solenoid valve on my 80W Co2 (Ruida RDC6442G).
As the documentation indicates, the solenoid valve needs to be connected between the 24V pin and the wind pin.
I am measuring around 16V between 24V and “Wind” at idle. When i start a job with Air Assist turned on (in layer settings and in vendor settings) it drops to around 14V. That does not seem right. Between 24V and Ground i am measuring 24V. Between 24V and “Status” im measuring 0V at idle and 24V during operation.
So should i hook my solenoid between 24V and “Status” instead? Or is my controller broken. Because the documentation clearly shows hooking the solenoid up to 24V and “Wind”, which also makes more sense, but the solenoid valve obviously will not work in this configuration.
I tested the solenoid valve seperatly with an external 24V source, and it works fine.
The RDC6442G manual says the output current on each pin is limited to 500 mA.
If the valve draws more than 500 mA at 24 V or if it does not include the clamp diode shown in the diagram, then it may have damaged the controller’s output transistor. If so, then the output will never work correctly again.
A DC-DC solid state relay requires much less current and can handle a robust valve without trouble. The reduced drive current for an SSR may allow a damaged transistor to “work”, although that’s not guaranteed.
You wire the SSR’s input terminals to the controller the same way as the valve. The valve then goes between +24 VDC and the relay, with the other relay terminal to GND. You can also wire +24 VDC directly to the SSR, the other SSR terminal to the valve, and the valve to GND.
I checked the valve beforehand, it draws 250mA and was advertised as already having a clamp diode by default. Maybe the output was already dead before (I bought the machine used)?
I like your method of using a SSR, but i was wondering if that will work on the original terminals, since it doesn’t look like it is switching anymore (well, it does, from 16V to 14V).
Do you think there is a chance of me soldering on a new transistor?
The difference between status and wind is that status goes low anytime the machine is in run mode or executing a layer. Wind only goes active low when the machine is executing a layer with air assist enabled.
I’d plug it into Status and see if it works.
If I remember correctly, Wind output has to be enabled within the Ruida. Did you do this?
If everything is correct, sometimes you loose the output transistor. People have fixed these but there is no schematics around.
I’ve never been in mine, but in a worst case, here is what I’ve been told. There are 4 outputs or sinks and I believe one of these four is where the failure occurred.
Ahh ok, i see. So the “Status” pin works independently from the air assist? I figured, since it’s near the “Wind” pin, it is also coupled to it to show that air assist is on.
Yes. Air Assist is enabled in both the vendor settings, and the layer settings.
It is possible, because the SSR requires much less current than the valve: if the transistor is slightly damaged so it cannot conduct the current required to operate the valve, it might still be able to handle the SSR current.
Basically, you have nothing to lose.
@jkwilborn and I have an ongoing disagreement on this matter: he has no qualms about just connecting the valves to the controller and I regard SSRs as a cheap way to protect an expensive controller. Both of us being reasonable people, you may take your pick.
But i’m still confused: To my understanding, if the machine is in idle, I should measure 0V between 24V and Wind. And when start a new job, i should measure 24?
Or am I very confused right now…
Assuming the output transistor is damaged, it cannot conduct enough current to pull the low side of the valve coil to GND as it should. As a result, the voltage remains higher than it should and the valve does not work.
If it were completely destroyed, it would conduct no current at all and the voltage would not change. I hope it’s not in that condition, but the only way to know is to use an SSR to see if the transistor can conduct enough current to run the SSR.
Most of the information I got came from the RDWorks site, so maybe you should go register and hunt around the laseruser forum and see if you can find anything.
I have little resources that reference the actual Ruida hardware… tough to come by.
These work by completing a ground for the device. Connecting 24V to the coil, then grounding the other lead should activate the device. If the transistor is damages it may look like there is a resistor between the device and ground resulting in a voltage drop.
Ah. That changes things. I assumed you were measuring the behavior of that pin with the valve connected.
The controller output is a transistor operating by switching current, but you’re measuring with an instrument designed to pass essentially no current at all. As a result, the voltage on the controller pin doesn’t behave as it will with the current through a real load.
If you have not yet connected the valve, you may choose believe either Jack or me concerning what you should do next.
It surely depends on the controller, but the RDC6442G manual says “All outputs are isolated through the optocoupler, and 500mA current for each, OC gate output”. I assume the output is a bare optocoupler transistor without a pullup, but I have certainly been wrong before.
If it has a pullup, then the voltage to ground should behave properly. Obviously, it doesn’t, but I can’t say whether that’s a damaged output transistor or a side effect of using a high-impedance voltmeter as a pullup resistor.
I know of no optical isolator that will switch 500mA. Sometimes I don’t have a lot of faith in the Chinese documentation.
If you know of a pcb pin or smd optical isolator that will will directly control 500mA, please post a link.
When people fix these, it’s one of the transistors I pointed out on the hardware. Notice they are all three pin devices, so they can’t be optical isolators.
A DC-DC SSR might count as a “power optoisolator”, because it’s basically an optoisolated power MOSFET, but it’s obviously overqualified as a controller output.
In any event, whether any particular output transistor has a pullup or not remains undecided; the doc isn’t forthcoming, so only measuring the controller’s behavior will show what happens.
A quick check of the OUT2 pin on my KT332N shows it’s “pulled up” to 6.35 V (‽‽‽ The +5 V controller pin shows 4.995 V) when it’s inactive, but a 10 kΩ resistor pulls it down to 0.05 V. AFAICT, the output transistor has a very high value “pullup” resistor, maybe 1 MΩ, so it’s pulled up, but not in any meaningful way.
