Maslow Home Maslow Community Garden Newsletter

Higher Voltage? 24V?

I’d like more feed speed, but with power output going >240 at 40ipm just going up, there’s not a lot of wiggle room (120", wooden top bar, bottom pulley, 22in above ply).

So… the motors are 24V (well, my MetalMaslow Z, so I’m assuming the other 2 are as well). The Arduino is 12V, and the TLE5206 can do 24V…

I’m thinking of powering the motors with a 24VDC, 15A adapter (this - https://amzn.to/397QR1t), and keeping 12V for the rest of the Arduino and shield stack (Arduino thinks their linear regulator will be most unhappy with 24Vin).

Has anybody run at 24V before and have some tips to make sure I don’t let the smoke out?
Does anyone have the TLE5206 boards in stock, or do I need to build one myself?

I have them in stock. If you burn it out I’ll send you an extra one for the cost of shipping. I’m curious what will happen to so don’t mind supporting your tinkering. Bar mentioned running the motors at 24v a long time ago. no one has done it.


if you do not need the arduino board, square tube housing or power supply the price will be $50 instead of $80 just buy it above and we can ship out on monday.
1 Like

when you test this, you will want to avoid the top middle center. you really need to have more than a 22" beam height when speeding up the motors to avoid stressing out the motors. better safe then sorry.

Was there some concern about the motor gear reduction plastic gears running with the higher torque at 24 V?

yes there was, which is why a bigger frame is necessary. The default 18" height of the motor bar generates too much force in the center middle area when the motors are run faster. It needs to be 30" or more for these forces to be small enough to not be a concern.

in general I recommend treated the maslow as more of a 4x5’ cnc and raising the bar to 30" above the cutting area. the forces are much better across the sheet and most users dont’ cut projets bigger than that typically from what I have seen.

minor correction, the Mega runs on 5v I believe there is a regulator on the
motor controller to drop the voltage to 5v to power the mega

technically motors from the same company that run on 24v are a different part
number, nobody has reported tests running the 12v motors on 24v. In practice I
think they are really identical.

David Lang

1 Like

The Mega runs off 5V, but the arduino board has the regulator, and Arduino says don’t put more than 18V into it… so I’m gong to cut the 12V line from the TLE5206 board to keep 24V off the Arduino (my Pi seems to be able to power it via USB, so I probably don’t even need 12V…).

I’ll use my bench supply at first and see what happens…
Let’s play with some power :wink:

2 Likes

You want to talk to @Gero about what happens with too much voltage. It has been done.

Thank you

1 Like

Missed you too, my friend, life is busy. When you put the bigger supply on and the motors broke your top rail. Beer is needed!

Thank you

1 Like

We are talking about higher voltage, not higher amps.
No one has ever tried 24v and posted about it in this forum that I am aware of.

Please accept my apologies for going off-topic, sort of. I was mentioned and just respectful enough to answer. I’ve deleted my posts and my experience with higher feed-rates will stay with me. I begin to understand why some old folks that have been with the Maslow since birth are not around any more, if this is the new attitude. Perhaps Bar can make you Moderator so you can delete post of guys that go shamelessly off-topic. It would be better the lecturing I think.

sorry I think you took it the wrong way. I was just clarifying that amps is different then volts. I’m not a motor expert, but my understanding is one could have a 100amp power supply but the motor will only take what it needs. Voltage on the other hand forces the motor to spin faster and generate more heat. thats’ all.

1 Like

The TLE5206 board does not allow 12v to pass to the Arduino, you can add a 24v power supply without damaging the Arduino.
Taking in account that the internal resistence of the motor’s coil will be the same, the ohm’s law tell us that the current WILL go up when we apply more voltage V/R = CURRENT
from 12v to 24v the current will be twice as before

1 Like

Sorry for taking it the wrong way. Am a little sensitive at the moment. I myself was wondering why Bee mentioned me with higher voltage. I clarified that I only went with higher Amps. With a heavy sled moving in a straight line across the top of the sheet I had a sag in the cut. It was assumed that the stock power-supply did not give enough Amps for the motor pulling to keep up with the motor feeding out. Was that the issue? I don’t know, but it disappeared after going to 10A. I have not tried higher voltage. I did temper with the max feedrate that is/or was hardcoded in the firmware.

1 Like

The maximum speed of the sled is not only determined by the speed of the motors. The motors can only pull on the sled, when it goes down gravity takes over, hence the bit type, router’s RPM, sled friction and the hardness of the wood you’re cutting needs to be taking in account as it will determine how fast we can cut in that direction, if the router can’t keep up it will probably jump off the wood.
To prevent this Maslow has very conservative parameters out of the box. One user can probably cut faster on softer plywood, while the same settings can be dangerous for another user that’s cutting harder wood.

If the voltage is applied constantly, then yes the current will go up.

but remember, the motors are driven via a PWM signal, so you aren’t applying the
voltage constantly.

David Lang

David
If he is using the same firmware, the PWM duty cycle that’s controlling the mosfet’s gate will be the same at any given time, hence doubling up on the voltage will increase the current x2 (maybe more due to gate capacitance?)
I think the idea of testing with more voltage is great and may work, we just need to test,

the pwm frequently will be the same, but the duty cycle will not be, the duty
cycle is dynamically controlled via a pair of nested PID loops, so as the higher
voltage moves the motors faster, the duty cycle will decrease.

So at the same speed, the power will be the same, which with higher voltage will
mean less current.

When you move faster, the power level will increase, but that’s not what I’m
talking about here.

David Lang

David

True

The duty cycle is what controls the speed of the motors, not the other way around.

The Arduino controls the speed via (PWM) mosfet’s gate which is kind of independent from the voltage that the shield supplies to the motors via drain/source. The firmware does not know what voltage is passing through the Mosfet drain/source, hence connecting 40v or 12v to the shield will not make any difference on what the Arduino sends via PWM to the gate.

What do you mean by “power level”?

The motors will move faster on 24v but the current will also increase. There is more than just winding resistance id dc motors, back emf plays a big role too, but basic ohm’s laws still apply.

I’m just trying to help here, i think testing with higher volts is worth a try, just keep an eye out on the power supply which my heat up.

the firmware decides what duty cycle to use on the PWM signal based on the
desired speed and position compared to the current speed and position of the
motor.

so if you feed the motor a higher voltage via the PWM, the firmware will reduce
the duty cycle so that the motor runs at the same speed.

It’s not that the firmware says “I should be running at X speed, let me look up
what PWM will produce that speed”, it’s that the firmware says “is the motor
running at the speed I want, if not increase/decrease the duty cycle”

David Lang