Acorn Power Supply Question

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TaylorPilot
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Acorn Power Supply Question

Post by TaylorPilot »

I am reading through the newly released manual and I noticed on page 33 it says not to use the same 24v power supply to power both the Acorn and the estop contactor. I have a larger meanwell din 24v power supply I am using to both supply power and power the contactor (with snubber). It seems to be working fine, but I don't want to damage something. What is the reasoning for not using the same power supply?
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Re: Acorn Power Supply Question

Post by eng199 »

The ACORN power supply should not power noisy things like contactor coils. Most often, the Estop loop is also AC. If it is working, that is fine. It is not the recommended way to go, so keep that in mind if weird stuff happens.
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Re: Acorn Power Supply Question

Post by TaylorPilot »

Ok, thanks. If need be, I will get another small one to power the acorn.
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Re: Acorn Power Supply Question

Post by Richards »

You can use a Meanwell MDR-20-24 (or larger) DIN rail mounted power supply to power ONLY the Acorn. The Acorn only draws 0.5A. Then, use another MDR-60-24 or MDR-100-24 power supply to power the Acorn's inputs and outputs. Make certain that you connect the -24 signals together. They are NOT -24, but just a common ground connection. (I wish that manufacturers didn't use -24 unless the power supply put out a -24vdc signal that was really -24VDC when referenced to GND.)

I have not had trouble using the same MDR-100-24 power supply for all +24VDC power in my system, but using two power supplies is good practice. The Meanwell MDR series power supplies are inexpensive. I always use a circuit breaker or fuse for every power supply. Depending on what the power supply powers, I sometimes install the fuse/circuit breaker on the input side of the power supply. Other times, I install the fuse on the output side of the power supply. Automationdirect.com sells DIN rail mount fuse holders such as the KN-F10L24DC-10 for 5mm fuses and the EHM1DU-12 for midget sized fuses.
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Re: Acorn Power Supply Question

Post by bleiler60 »

Hello Richards,
Your post said that the -24v should be connected together. Just to be clear the -24v from each power supply should be connected together?

I just finished building a control cabinet with 2 power supplies. The Acorn board has it's own power supply and the second power supply is for everything else.

Each power supply has it's own terminal strip for the -24v. is this wrong?

Thanks Bill
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Re: Acorn Power Supply Question

Post by Richards »

When using a Meanwell MDR series power supply, the +V terminal is +24VDC. The -V terminal is GND or COMMON. The terminal label is misleading.

When using multiple power supplies, connect the -V terminals to GND or COMMON so that they form a common reference point. Do not connect the +V terminals from multiple power supplies together. Let the +V sides float so that they don't compete against each other.

For instance, on one MDR power supply, connect +V to the Acorn's +24VDC input. Connect the power supply's -V terminal to Acorn COMMON. Connect the power supply's AC Ground (chassis ground symbol) to Chassis Ground on the Acorn (which is internally connected to COMMON or GND). On the other power supply, connect the -V to Acorn COMMON and to the cabinet's terminal blocks that are COMMON or GND in your build. Connect the +V to H1 or H4 +24VDC (they are connected together internally on the Acorn board). Also, connect the +V on the second power supply to anything external of the Acorn that requires +24VDC.

One power supply powers the Acorn only. The other power supply powers the Acorn's inputs plus anything else in your cabinet that requires +24VDC.
-Mike Richards
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Re: Acorn Power Supply Question

Post by firebrick43 »

Can you use a 70w plus power supply, say a Meanwell NDR-75-24, to power both the acorn and the ether1616 together?. Another PS to power all other 24 volt coils. It would save space in the cabinet. Thank you
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Re: Acorn Power Supply Question

Post by Gary Campbell »

As stated above, you should use a separate power supply for items that can induce noise, such as contactors, relays, and solenoid valves.
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Re: Acorn Power Supply Question

Post by firebrick43 »

Gary Campbell wrote: Sun Jan 16, 2022 11:52 am As stated above, you should use a separate power supply for items that can induce noise, such as contactors, relays, and solenoid valves.
But will the ether1616 generate noise for the acorn MPU? It does have relays, but so does the 8 relay board that comes with the acorn.

I very specifically stated that I would use a separate power supply for the contactors and solenoids.
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Re: Acorn Power Supply Question

Post by centroidsupport »

Both both 8 relay board and Ether1616 have flyback doides on all the relays to reduce noise
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
https://www.centroidcnc.com/centroid_di ... _gear.html
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