Sculptfun S9 DC Power Option

Just recently setup one of these bad boys to play with and I’m wondering if anyone has tried to run one off of DC power. The controller says it runs 12v@3A, but the power supply is an AC unit that runs 12v@5A (for 60w). Looking to cut the power loss wasted in the excess of the power brick as well as the AC to DC conversion. Anyone have experience with this as of yet?

Welcome back!

Not clear to me what you want to do.
I would expect that DC is DC however you get it :slight_smile:
If you eliminate the brick how will you develop the DC?
Unless you are using batteries there has to be an ac to dc conversion?

Would I not need to match voltage or amperage to avoid frying components or anything? I’d imagine I couldn’t just plug a dc to dc cable into, say, a Jackery portable power station and it would presumably just work…or could I? If the source output is roughly 12v and the amperage is at or over 3, it should be fine, right? Would it be an issue if the source were 18v or 24v? Just trying to make sure i don’t assume the wrong thing and break it before i really get to use it.

What is wrong with the supply that came with it?

Nothing is wrong with the original power supply. I just want to use DC power and not waste energy on the conversion.

I’m curious what power source you have that doesn’t involve conversion. Even if you have a DC solar system, you probably have a DC-DC buck/boost converter involved in charging batteries to maintain correct charging voltage, and both the DC-DC conversion in the charging system and battery storage are each individually not 100% efficient.

Switching AC-DC power supplies are quite efficient, and they are conceptually similar to DC-DC buck converters. Switching power supplies with power factor correction can be over 90% efficient. Cheaper supplies without power factor correction do waste some “imaginary” power (which isn’t actually imaginary, it means they aren’t phase-matched) but are still over 80% efficient. (“Imaginary” power is typically not charged to residential customers but typically is charged to larger commercial customers. This is why businesses can save money by buying more expensive but more efficient power supplies, but residential customers typically can’t.)

Charging a battery from the grid and then discharging it is likewise less efficient than just using a switching power supply in the first place. Guess what they use to charge the battery!

(Thermodynamics. You can’t win. You can’t break even. You can’t even get out of the game. :smiley:)

Ultimately this will be in a battery powered off-grid situation. My desire is to minimize energy loss wherever possible to maximize usage time. 80% efficient wont cut it if it means I lose 2 or 3 hours in a day of general usage. Also, the more energy lost in conversions and such, the faster the batteries drain… meaning the more often batteries will run low, which is bad for them long term.

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If you have a 12V battery solar-charged system, then you should be fine. You’ll have additional down-regulation on the board anyway; the processor isn’t running at 12V!

you mentioned the controller stating its input power requirements are 12V @ 3A but what is the machine max requirement? This will be with max speed( or accelerating) and 100% laser power.
When you figure that out you will then have a number to start looking at for battery size. You will also have to look at if that input voltage is 12V regulated or if it can swing as high as 14V which is what you’ll get with charging lead acid batteries. And a lead acid battery at 12V is a fully depleted battery so it should always be run and stopped before it hits 12.0VDC.

Worry about efficiency after you understand your power and runtime needs in order to determine battery capacity and therefore solar charging needs. As @mcdanlj mentioned, there’s already lots of power conversions going on so worrying about a few percentages in a switching powersupply will kill the project before its even started.

Appreciate the input. I shall chew on this for a bit.

The logic will have a regulator in front of it, and the LED will be current-controlled at least and quite possibly also regulated, so a ~14V full charge for a lead-acid battery (exact voltage depends on chemistry; e.g. gel cells are lower than wet) is very likely just fine. No guarantees, but it’s a reasonable expectation and if it were my money it’s a bet I’d take. You pays your money and takes your chances, I’m no electrical engineer, so I’m not responsible for any smoke, but… :smiley:

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Want to post a high-resolution picture of the control board?

Some S9s appear to have used a modified clone of an MKS DLC v1 which only supported 12V, but if they’ve upgraded to a v2 derivative then it could be 12-24V tolerant since the MKS DLC v2 supports 12-24V input.

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Unfortunately its enclosed and I don’t know if opening the casing would void any warranty I may have. Any way I can check that without opening it up?

I don’t have any unit from them, just going from what others have posted.

You could use a DC-DC stepdown converter, but those have a minimum drop (depends on the unit) and some can be damaged by back-EMF (from the stepper motors) which might require a diode to block and add to the minimum voltage drop required. Being able to run only on a completely full battery wouldn’t help you much!

BTW, You can add to the list of things unlikely to be damaged by 14V the steppers — like the LED those are current-limited and current is the main factor for motors generally.

The challenge with running over 12V (@14V) may be heat and performance. This is especially true if this is running in an environment above ambient [really hot right now].

In some ways the increase (17%) may enhance performance, in other circuits it may allow operation above limits. Many of these controllers are running in marginal territory without heatsinks at the nominal voltage. This is less of a concern if the board is spec’d at 12-24VDC

Another consideration is how clean the DC power is when its charging batteries. Some chargers do not care much about HF noise at the battery.

Most modern solar systems do not connect the load, even DC loads, directly to the battery for exactly the reasons above. Lithium batteries have important charging profiles that may not be kind to directly connected loads. Many charge controllers have a filtered and isolated 12 and 5V (USB) DC outputs as do many inverters.

If your overall application is trying to avoid any kind of AC conversion from DC it’s easy enough to put a regulator on the battery. As @mcdanlj suggests you will have to pay attention to drop out specs.

If any AC is required you will need an inverter and adding a brick with a DC output of 12V @ 3a will only add < than an amp at 120V. Not worth considering. In this case the inefficiency is in both the inverter and the brick.

Lastly I agree with others that you should budget out all the power in the system with operating current measurements before you make a final choice.

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Every part of what @donkjr says about battery charging is really meaningful not just to this but to any direct use of batteries while they are being charged.

Warning: I’m a programmer not an EE. If @donkjr says I’m wrong about any of this, he’s more likely to be right than I am, because what I’ve learned about this is all self-taught.

Thinking through the current regulation of the parts of the system: The current limiting for the stepper motors is efficient (done by regulating full-voltage pulses rather than dropping voltage across a resistor); this is a feature of all modern stepper driver chips. For the LED laser, current limiting is almost certainly a transistor current source, so essentially a variable resistor. For the logic, there’s possibly a DC-DC buck converter on the board, but whether or not there is one, there will be a low drop-out (LDO) voltage regulator which is again essentially a variable resistor. However, the current consumed by the logic will be vastly less than the steppers or laser, so the difference in efficiency between 12V and ~14V will be proportionally small for the logic power supply on the board.

Note that cheap DC-AC inverters not intended for motor applications also don’t have phase compensation, so are perfect for feeding AC-DC converters; it’s capacitors on both sides so you don’t need phase-matching — this is why they are advertised as not to be used for motors; they don’t work well for inductive (basically, electromagnetic) loads. This means that a switching power supply that is normally 80% efficient might actually be more efficient when running off a cheap AC-DC inverter than when running off grid power! (I don’t know this part for sure; I’m imagining based on my limited knowledge.)

My guess is that if you are worried about warranty, they are just as likely to complain about you not using their power supply as they are about opening a case. I don’t know whether they have a reputation for honoring warranty claims, so I don’t know to what extent this distinction is practical. :smiley: