Linear Mode Power Supply

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Asadinator
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Linear Mode Power Supply

Post by Asadinator » Wed Apr 25, 2018 9:38 am

For a specific application where I am using high frequency device with the printer, I require a linear mode power supply to power the extruder heater mosfets. The switching mode power supply just would not work.

Does Makergear provide a linear mode PSU? I suspect it would be larger.

Or does anyone have a tip of an external PSU I can use for the RAMBo on the Makergear M2 printer?

Cheers

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ednisley
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Re: Linear Mode Power Supply

Post by ednisley » Wed Apr 25, 2018 2:19 pm

Asadinator wrote:a linear mode power supply
High-power linear supplies are obsolete for consumer-grade applications, so finding a supply with enough output current for the platform heater will be ... difficult.

Verify the printer's actual current before spending any money. The platform heater accounts for most of the current and is easy to measure, but the hot end's PWM switching requires more care: measure at 100% duty cycle while it's heating from room temperature to find the actual current. Double whatever you've set for stepper currents and it'll be about right.

A quick eBay check shows some 24 V linear supplies available for high-end audio gear, with prices to match:

https://www.ebay.com/itm/TeraDak-DC-200 ... 3118305424

Using this triple-output lab supply with independent outputs seems feasible:

https://www.ebay.com/itm/Dr-meter-HY300 ... 2921895328

If you can keep it cool, a boat anchor might do the trick:

https://www.ebay.com/itm/Lambda-Model-L ... 2984277959

OK, so what are you building? [grin]

Asadinator
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Re: Linear Mode Power Supply

Post by Asadinator » Wed Apr 25, 2018 3:02 pm

Thanks Ed, those were the type of PSUs I was looking at as well.

Instead of extrusion with FDM, I am powering an ultrasound transducer via other circuitry.
I’m not sure whether I require a heat bed. Transducer won’t use more than about 2-3A.
Let’s say I use a 5A linear PSU to power the Rambo, will it simply cause the heat bed to heat slower?
Is it possible to use a single output PSU to power the Rambo? Will it cause the motors problems?
Or should I go for the triple output and power the 3 inputs independently?
My other option is two use both the Makergear PSU for heatbed and motors, whilst linear PSU for extruder/fans.

Cheers

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insta
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Re: Linear Mode Power Supply

Post by insta » Wed Apr 25, 2018 5:37 pm

Use your other option. There are 3 sets of wires going into RAMBo's power supply -- the top set (nearest the blue fuse) are -/+ heater, then the next two are -/+ heaters/logic, and the last two are -/+ for the motors. Remove the middle two wires and use your own linear supply.

That said, I'm on Ed's side here. Why is the stock PSU not working, outside of the wrong voltage? They are name-brand Meanwell supplies and have very clean outputs.
Custom 3D printing for you or your business -- quote [at] pingring.org

Asadinator
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Re: Linear Mode Power Supply

Post by Asadinator » Wed Apr 25, 2018 10:23 pm

insta wrote:Use your other option. There are 3 sets of wires going into RAMBo's power supply -- the top set (nearest the blue fuse) are -/+ heater, then the next two are -/+ heaters/logic, and the last two are -/+ for the motors. Remove the middle two wires and use your own linear supply.

That said, I'm on Ed's side here. Why is the stock PSU not working, outside of the wrong voltage? They are name-brand Meanwell supplies and have very clean outputs.
I can’t find the switching frequency of the Meanwell PSU, but I need to operate a signal generator and amplifier at 2MHz.
The supplier of the transducer has said not to use switching mode PSU.
I can give it a try though and see what happens :D

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ednisley
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Re: Linear Mode Power Supply

Post by ednisley » Thu Apr 26, 2018 2:26 am

Asadinator wrote:Let’s say I use a 5A linear PSU to power the Rambo, will it simply cause the heat bed to heat slower?
The platform heater will overload the power supply, which will promptly shut down.
The supplier of the transducer has said not to use switching mode PSU
I'd expect a 75 W ultrasonic emitter (heater?) to introduce hellish noise back to the power supply lines, so running anything else from that same supply seems like a Bad Idea.

Conversely, if you're listening for ultrasonic echoes, you're definitely gonna hate the hash introduced into your receiver by the steppers and PWMed fans; the RAMBo board's signal management isn't up to RF specs.

From pieces you've mentioned here and in other threads, IMO you should reconsider the whole "Let's hack a 3D printer into an ultrasonic death ray" plan. The whole lashup will have many, many mysterious ways to not work, apart from the obvious power / noise / G-Code / control issues.

Perhaps starting from a small CNC machine, rather than a 3D printer, with additional electronics designed for and capable of doing what you want, will produce a better result.

I loves me my M2, because it's a great 3D printer, not a plotter, laser engraver, vinyl cutter, or death ray ...

Asadinator
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Re: Linear Mode Power Supply

Post by Asadinator » Thu Apr 26, 2018 3:41 am

ednisley wrote:
Asadinator wrote:Let’s say I use a 5A linear PSU to power the Rambo, will it simply cause the heat bed to heat slower?
The platform heater will overload the power supply, which will promptly shut down.
The supplier of the transducer has said not to use switching mode PSU
I'd expect a 75 W ultrasonic emitter (heater?) to introduce hellish noise back to the power supply lines, so running anything else from that same supply seems like a Bad Idea.

Conversely, if you're listening for ultrasonic echoes, you're definitely gonna hate the hash introduced into your receiver by the steppers and PWMed fans; the RAMBo board's signal management isn't up to RF specs.

From pieces you've mentioned here and in other threads, IMO you should reconsider the whole "Let's hack a 3D printer into an ultrasonic death ray" plan. The whole lashup will have many, many mysterious ways to not work, apart from the obvious power / noise / G-Code / control issues.

Perhaps starting from a small CNC machine, rather than a 3D printer, with additional electronics designed for and capable of doing what you want, will produce a better result.

I loves me my M2, because it's a great 3D printer, not a plotter, laser engraver, vinyl cutter, or death ray ...
Only reason I’m using a M2 is because I have had it for a while and familiar with it :) easiest way to test a death ray prototype hehe. And I have no use for it currently.

Perhaps I can forget about the heater bed if I’m going to power from a single linear PSU.

It’s not a listening device, just output, funnily at 75W as you mentioned.
There are 3 levels of circuitry after the Rambo output and before transducer:
- signal generator (perhaps using a fan output to always stay on)
- power amplifier (extruder heat output)
- impedance matching unit

Hope it doesn’t introduce noise to seriously disturb other components.

Asadinator
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Joined: Tue May 13, 2014 3:24 pm

Re: Linear Mode Power Supply

Post by Asadinator » Fri Apr 27, 2018 2:29 pm

After further discussion with supplier, apart from noise it seems a switching mode power supply would still work for my application.

That’s a relief. Thanks for your help anyway gents.

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