External 5v Source
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@bearer said in External 5v Source:
(You'll want to check the current rating for 5v standby if you plan on using it for the pi)
I'm changing my mind on that. I think I'll just feed the Pi 4 directly with a separate 5v power supply set to 5.2v and have the Pi provide 5v to the Duet 3 via the ribbon cable. My tests with that setup have been successful, and I get better 5v on the Duet 3 than with the onboard converter, despite the resistance in the ribbon cable. The Duet 3 draws barely any current over 5v anyways, and this is one of the "supported" modes so I won't be running afoul of the "rules"
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@bearer said in External 5v Source:
Haven't checked the code or measured the signal, but from the behaviour on the one printer I have set up with a ATX supply it does seems so. On power on the ATX supply only provide 5v standby until you turn on the ps_on output (pulling it low) and then you get 12v Vin.
I'm trying to set it up to work in reverse. That option is supposedly on the to-do list for the 3.x firmware series, but I haven't seen it in the 3.2 changelog so far so I'm assuming it didn't make it yet. I've been trying to figure out how to get it to provide 5v when pulled high, but I'm not sure how to go about it... I was considering a high pullup resistor between the 5v and ps_on pins
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Reverse? For the ATX supply or the output? Yes, the output will support inverting the signal to support some Meanwell supplies i think.
The ATX supply will need modification to work otherwise, or simpler throw a 5v relay in there and always on the supply.
You can't supply any serious current through a pull up resistor btw.
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@bearer I'm using a Meanwell power supply with remote control, hence the need to reverse the behavior.
So if I understand correctly, if I add a resistor (say, 10k?) between the 5v and ps_on pins, then when ps_on is floating (M80), it'll provide 5v but when it's pulled low (M81), it'll provide 0v? That way I could connect the - (minus) pin of the Meanwell remote control to the GND pin and the M80 and M81 commands would function as expected?
I'm hurting my brain...
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@GoremanX I think you've tied your brain in knots.
The board powers up in a floating state.
M80 switches a power supply (that has an active-low input) on by pulling pson low.
M81 switches a power supply (that has a active-low input and its own pullup) off by letting pson float.
If you add a pull-up resistor to 5V it will power up at 5V, then when you issue M80 it will go low. As to whether this casuses your PSU to do what you want depends on the PSU. You mention a Meanwell RS-25-5, but I don't think that has a input that will work with pson - it's just on when mains is supplied and off when not.
In my system I have an opto-isolator across 5V and pson. That activates a relay. Yes it has a flyback diode.
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@achrn My 24v power supply is a Meanwell RSP-150-24, that's the one I'm trying to control with the ps-on pin. The remote control pins on that power supply function in reverse to an ATX power supply
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Possibly stupid question: If I use an external 5V PSU, do I need to remove the INT_5V jumper?
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@GoremanX said in External 5v Source:
RSP-150-24
Ah, of course - I was being stupid thinking it was the 5V you'd control with pson.
However, my reading of the RSP-150-24 data sheet shows it as active low, same as a ATX. The data sheet I've found says "CN1: < 0~0.8VDC POWER ON , 4~10VDC POWER OFF".
So yes, I think you could connect a pullup between pson and +5V, then connect pson to CN+ and ground to CN-. I don't know what current that needs - 10k might be a bit high- I'd probbaly start at 1k.
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@oliof Yes. If you're feeding 5v to the board from an external source (either from a Pi or through the ext_5v pin), then you no longer need to use the onboard 5v converter. Removing that jumper disables the onboard converter
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Just think of the mosfet (the device controlling the pin) as a switch between the pin and GND.
When you issue an M80, the switch closed, so there is a path to GND.
When you issue an M81, the switch opens, so there is not path to any of the power levels.
As far as i know, you can't change this behaviour (use m81 to "close" the pin) so if you need to control a device that is active high you will need external circuitry like a 7404).
What you can do, is changing the default state. If you want your duet to power on as soon as it is supplied power, just add M80 to your con fig.g
If you want your duet to start powered down (i mean the ps_on signal) you don't have to do anything, but you should add M81 in your con fig.g, so the power control appears in your duet web control interface (in RRF3 the ATC power control block won't appear until you have issued a m80 or m81 command)
and lastly @oliof YES if you feed 5v via the ext 5v header you have to remove the int_5v jumper.
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@achrn Woohoo! That worked. Ended up going with a 100ohm pull up resistor, and it works great. Anything higher would cut the voltage down below the 4v threshold for the remote control. The draw from the mosfet doing the switching on the power supply is negligible, so my tiny 1/4 watt resistor isn't being stressed at all. I'll wrap it in heat shrink tubing and call it done.
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@GoremanX said in External 5v Source:
my tiny 1/4 watt resistor isn't being stressed at all.
unless I'm missing something it will be when ps_on is pulled to ground? 100 ohm and 5v = 250mW no?
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@bearer oohh, maybe. Good call. Technically that's exactly its capacity and it hasn't been an issue so far, but it might be in the long run. Could try 220 ohm instead and that would be half its capacity. 1kohm was definitely too high, I was getting just over 3v and it wasn't enough to turn off the power supply.
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(just keep an eye on the temp)
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@bearer switched to a 220 ohm resistor. The voltage to the ps_on pin is now 3.7v, but that seems to be enough to turn off the power supply despite being under 4v. This setup works great. Obviously I'd rather have M80 and M81 work in reverse, somehow, but this will do.
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I think that is the feature on the to-do list to allow inverting the pin, so M80 and M81 will work as expected.
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@GoremanX I don't think reversing M80 / M81 helps.
With it reversed, the pin will be low when the Duet wants power to be off, and floating when the duet wants power to be on. That doesn't help you.
At the moment you have a PSU that switches on when a pin is pulled low, and you have a Duet that pulls a pin low when it wants a PSU to switch on. That sounds like a match to me. Why do you want one of them reversed?
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@achrn said in External 5v Source:
At the moment you have a PSU that switches on when a pin is pulled low,
he said the opposite in his last post? which i assumed is what all the fuss with the meanwell psu's a while back was all about as well
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@achrn With M80/M81 reversed, I can connect the + (plus) from the remote control to the EXT_5V pin, and the - (minus) to the ps_on, and then switch the power supply off by switching its - (minus) between pulled low and floating, no pullup resistor needed. In fact, this already works when I wire it up that way. M80 turns off the power supply and M81 turns it on (which is backwards)
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@GoremanX Thanks, I understand now.
