Converting 12v to 24v

[FRCTEAM1847]

If the clutch is utilizing a solenoid to accomplish it's task, then R42 (power distribution), R47(custom circuits can't alter voltage), R48J(solenoids must be 10W @ 12V), and R50E (can be hooked up to a Solenoid breakout board which is powered by 12V) combine to say that a 24V electric solenoid is specifically prohibited.

That being said, I would still go to Q&A though.

[Johnny_5]

The electromagnetic clutch doesn't operate with a solenoid, I have attached a wikipedia article about how they work.

http://en.wikipedia.org/wiki/Electromagnetic_clutch

I will follow up with the GDC Q&A forum to find out if it is legal

[Al Skierkiewicz]

Issac,
The clutch you linked to specifically discusses the attraction of an armature plate by the magnetic field set up when the field coil is energized. It attracts the armature to a frictional coupling with the driver mechanism. This is exactly what an electric solenoid actuator is and therefore must conform to the solenoid rule, 10 watts @ 12 volts continuous. This is much different than an eddy current clutch where no parts move and no friction is used in the transfer of power.

[Tristan Lall]

Originally Posted by Al Skierkiewicz

Issac,
The clutch you linked to specifically discusses the attraction of an armature plate by the magnetic field set up when the field coil is energized. It attracts the armature to a frictional coupling with the driver mechanism. This is exactly what an electric solenoid actuator is and therefore must conform to the solenoid rule, 10 watts @ 12 volts continuous. This is much different than an eddy current clutch where no parts move and no friction is used in the transfer of power.

There might be a distinction. I believe that in a solenoid actuator (of the conventional commercial type) the axis of the wrapped wire coil (not the wire itself) is coincident with the central axis of the armature (generally a shaft or similar). The armature moves within the central void.

In this design, it looks like the coil might be instead wrapped around a circular axis (i.e. toroidally). In that case, the armature is not moved within the centre of the coil. It wouldn't be a solenoid (even a toroidal one, if that's even possible), because there is no open core within the windings of the coil.

I can't tell exactly what's going on the diagrams, but here's another cutaway for comparison:

Scag Power Equipment

[Al Skierkiewicz]

Tristan,
You forget the test we have used for this in the past. If it is a coil and something moves when you apply current, it is considered a solenoid/electric actuator. It is strictly limited by the GDC to limit the power sources that can be used on a robot.

[Tristan Lall]

Originally Posted by Al Skierkiewicz

You forget the test we have used for this in the past. If it is a coil and something moves when you apply current, it is considered a solenoid/electric actuator. It is strictly limited by the GDC to limit the power sources that can be used on a robot.

I didn't forget that test...but I don't like the way it conflates a solenoid with an electromagnetic actuator as if they're necessarily the same thing. Here's an example of something which is clearly an actuator, but also clearly not a solenoid:

Originally Posted by Tristan Lall

Just for the sake of discussion, is this electromagnetic bell a prohibited solenoid actuator? (I would say no, because its geometry is inconsistent with a solenoid.)


From Wikimedia Commons

For the first time, it looks clear that FIRST wants to regulate all electromagnetic actuators (per the rule change noted in a previous post). But in that case, why not subclassify them as motors and non-motors? Is there something special about a solenoid actuator that doesn't apply to another kind of electromagnet that does mechanical work?

And while it's a convenient distinction, what would FIRST's rationale be for caring about whether a device does mechanical work or not? There's no correlation with electric power input, and there's no guarantee that a device not designed to do work is inherently safer than one that is.

Despite my concern with the rationale, given the rules this year, the way I think the test should work is as follows:

• Is the device electromagnetic and an actuator? If (and only if) so, [R48] applies.¹
• Does it contain a motor? Then see [R48A-I, K-L].
• Does it contain a solenoid? Then see [R48J].
• For electromagnetic actuators not otherwise mentioned, there is no specific permission (required because these are "[t]he only motors and actuators permitted"), thus they are illegal.

Following that logic, the electromagnetic bell (not a solenoid) above was legal in 2010, but is illegal in 2012. Similarly, an electromagnetic clutch which is not a solenoid is illegal this year (but would have been legal in some previous years). An electromagnetic clutch which is a solenoid is legal this year, provided it conforms to the solenoid rule.

¹ Despite its wording, [R48] appears to apply to electromagnetic actuators...if that weren't true, there would be a rules conflict for pneumatic actuators.

[Al Skierkiewicz]

Are you saying that the bell is not doing work? Is not a solenoid? How was the bell legal in 2010?

2010 Robot Rules...
<R53> Items specifically PROHIBITED from use on the ROBOT include:
A. Electric motors and/or servos different from, or in addition to, those in the KOP, with the exception of those specifically permitted by Rule <R52>.
B. Electric solenoid actuators (note: electric solenoid actuators are NOT the same as pneumatic solenoid valves – the latter are permitted, the former are not).

[Tristan Lall]

Originally Posted by Al Skierkiewicz

Are you saying that the bell is not doing work? Is not a solenoid? How was the bell legal in 2010?

The bell is:

• electrical,
• an actuator,
• not a solenoid, and
• doing work.

There was no prohibition against electric actuators in 2010, except that motors other than those listed were illegal, and solenoid actuators were illegal. Think of it as a custom circuit. (It must still comply with all other rules.)

(The 2012 rules are somewhat different, as noted above.)

[PAR_WIG1350]

Originally Posted by Tristan Lall

The bell is:

• electrical,
• an actuator,
• not a solenoid, and
• doing work.

There was no prohibition against electric actuators in 2010, except that motors other than those listed were illegal, and solenoid actuators were illegal. Think of it as a custom circuit. (It must still comply with all other rules.)

(The 2012 rules are somewhat different, as noted above.)

A solenoid is simply a coil of conductive material (Technically, there are many accidental solenoids on robots every year, but those are not actuators). The bell pictured clearly utilizes a pair of solenoids wrapped around the iron core. As stated it is an actuator. The actuation occurs as a result of current passing through said solenoids, thus, it is a solenoid actuator.

[Tristan Lall]

Originally Posted by PAR_WIG1350

A solenoid is simply a coil of conductive material (Technically, there are many accidental solenoids on robots every year, but those are not actuators). The bell pictured clearly utilizes a pair of solenoids wrapped around the iron core. As stated it is an actuator. The actuation occurs as a result of current passing through said solenoids, thus, it is a solenoid actuator.

A solenoid is a particular kind of wire coil: it's oriented such that it produces a uniform magnetic field within the core.

For sufficiently lax definitions of "uniform", sure, we've got all sorts of solenoids. But then you get into perverse situations where every motor winding is a rudimentary solenoid, and thus the motor is a solenoid actuator as well as a motor. (I, for one, certainly don't want to believe that this is what FIRST intended. It kind of flies in the face of conventional nomenclature, both for motors and solenoids.)

For the bell and the clutch, if the windings are squarishly wound around a squarish core (in cross-section), the magnetic field will likely be very non-uniform. That's also a poor approximation of a solenoid.

Contrast this with an ordinary solenoid actuator, which does indeed contain a tightly-wound cylindrical coil of wire, designed to provide a uniform magnetic field within the core.

I don't really see any way to judge from the rules that the level of non-uniformity found in the clutch's magnetic field is substantially different from the non-uniformity of magnetic field produced by a motor's windings.

[Al Skierkiewicz]

Tristan,
The bell was not legal in 2010. And there is no way anyone can convince me it's a custom circuit. The bell meets none of the criteria below that would make it allowed. And in all likelihood I would also rule it illegal under R02.

8.3.7 Motors & Actuators
<R52> Motors specifically permitted on 2010 FRC ROBOTS include:
A. All motors, actuators, and servos listed in the 2010 KOP,
B. An unlimited number of COTS servos with a maximum output torque of 55 oz-in and maximum rotational speed of 100 rpm at 6 Vdc (e.g. HITEC model HS-322HD or HS-325HB servos, as provided in the KOP),
C. An unlimited number of FIRST Tech Challenge (FTC) servos (HITEC HS-475HB servos),
D. One, two, or three additional 2½” CIM motors (part #FR801-001 and/or M4-R0062-12) in addition to those provided in the KOP. This means that up to five, and no more, 2½” CIM motors can be used on the ROBOT.
E. Identical one-to-one SPARE PARTS for motors, actuators, and servos provided in the 2010 KOP that may have failed or become damaged.

<R02> ROBOT parts shall not be made from hazardous materials, be unsafe, or cause an unsafe condition. Items specifically PROHIBITED from use on the ROBOT include (but are not limited to):
B. Speakers, sirens, air horns, or other audio devices that generate sound at a level sufficient to be a distraction or hindrance affecting the outcome of a MATCH

[Tristan Lall]

Originally Posted by Al Skierkiewicz

The bell was not legal in 2010. And there is no way anyone can convince me it's a custom circuit. The bell meets none of the criteria below that would make it allowed.

Remember that in 2010, the electric motor/acutator rules specified what was allowed (in terms of motors), what was not allowed (in terms of motors and solenoids), and was silent about all other types of electric actuators. The 2010 rule stated neither prohibition nor permission, and thus, per standard practice, it could be used if it also conformed to all other rules. I don't think we would disagree that—at least since the demise of the additional hardware list about a decade ago—teams can use parts that are not mentioned, provided they comply with all rules.

(For everyone else following along, be warned that the rule is different in 2012, because it directly addresses all actuators.)

And if not a custom circuit, what is it? It's a part which is legally connected to the robot electrical system (assume it runs through a Spike), but which is not specified in any official drawings/manuals. It affects no output devices nor power pathways, interferes with no other robots and is a COTS item. It's the same as an LED ring light in that respect.

Besides, other than the safety rules addressed below, what 2010 rules would you use to regulate this bell if it was neither a prohibited actuator, nor a custom circuit?

Originally Posted by Al Skierkiewicz

And in all likelihood I would also rule it illegal under R02.

The applicability of 2010's <R02B> (and I guess <R03A>) would depend on the implementation. It could be a factor if the bell was operating at or above its design voltage, and was unmuffled. Then again, if a team used a 24 V bell at 12 V, or stuffed a rag in the bell as a muffler, or just used the actuator part without the bell, it could easily conform to <R02B>.

[PAR_WIG1350]

Originally Posted by Tristan Lall

A solenoid is a particular kind of wire coil: it's oriented such that it produces a uniform magnetic field within the core.

For sufficiently lax definitions of "uniform", sure, we've got all sorts of solenoids. But then you get into perverse situations where every motor winding is a rudimentary solenoid, and thus the motor is a solenoid actuator as well as a motor. (I, for one, certainly don't want to believe that this is what FIRST intended. It kind of flies in the face of conventional nomenclature, both for motors and solenoids.)

For the bell and the clutch, if the windings are squarishly wound around a squarish core (in cross-section), the magnetic field will likely be very non-uniform. That's also a poor approximation of a solenoid.

Contrast this with an ordinary solenoid actuator, which does indeed contain a tightly-wound cylindrical coil of wire, designed to provide a uniform magnetic field within the core.

I don't really see any way to judge from the rules that the level of non-uniformity found in the clutch's magnetic field is substantially different from the non-uniformity of magnetic field produced by a motor's windings.

It'a a 2 dimensional drawing, the winding could be pentagonal for all I know. The only thing I can tell from the drawing is that what I can see of the coil is fairly uniform.

Additionally, even by your questionably strict definition of a solenoid, the sectioned clutch image you posted depicts what is quite clearly a solenoid. one side of the clutch is connected to a V-belt pulley (green) the other side is (yellow) is the armature of the solenoid which appears to move on a double keyed shaft. The solenoid winding are stationary and contained within a frame (grey). When the solenoid is energized, the armature is pushed out of the center of the solenoid winding to increase the friction between it and the green side of the clutch. The windings are co-axial with all components of the clutch and are wound as a single coil around the armature. That is, the coil of the clutch is a uniform, tightly wound cylindrical coil designed to provide a uniform magnetic field within its core.

[anthonyttu]

To preform (my understanding) what your trying to accomplish without breaking any rules or even flirting with any of them. You might look into pneumatic clutches. If your not using any pneumatic's anywhere else on the robot it might not be a good solution for your problem. Just an idea.

[Tristan Lall]

Originally Posted by PAR_WIG1350

Additionally, even by your questionably strict definition of a solenoid, the sectioned clutch image you posted depicts what is quite clearly a solenoid. one side of the clutch is connected to a V-belt pulley (green) the other side is (yellow) is the armature of the solenoid which appears to move on a double keyed shaft. The solenoid winding are stationary and contained within a frame (grey). When the solenoid is energized, the armature is pushed out of the center of the solenoid winding to increase the friction between it and the green side of the clutch. The windings are co-axial with all components of the clutch and are wound as a single coil around the armature. That is, the coil of the clutch is a uniform, tightly wound cylindrical coil designed to provide a uniform magnetic field within its core.

You may be right about the coil arrangement in the diagram. It could be toroidal, or it could be cylindrical, with several layers. If it is cylindrical, you could definitely have a viable solenoid within the bore of the clutch.

But, notice that the green armature does not reside inside the core of the windings. That's because it's arranged just like a conventional electromagnet (where the disc-shaped faces of the coil housing and armature attract), rather than a solenoid actuator (where the armature would be attracted/repelled by a portion running through the core of the winding).

And that goes back to the previous question: if we have a solenoid in an actuator, is it necessarily a solenoid actuator? If we have a decent solenoid in a motor winding, but the motor's principle of operation doesn't depend on the thing being a solenoid, is the motor a solenoid actuator? Same question here—even if we have a decent solenoid, the principle of operation of the clutch depends only on the external magnetic field. So why would this one be a solenoid actuator, if the motor isn't?

There's another layer of complexity: there's what I think, and then there's what I think a team could reasonably think. In this case, I think it's not a solenoid actuator. But I do leave open the possibility that a team might be under a reasonable impression that it is. (That would be highly dependent upon the situation, and the explanation and documentation provided.) I'm not saying this to be argumentative—I've got a better reason. It's the principle that a team that shows up to a regional having bought and installed an electromagnetic clutch should get the benefit of the most lenient yet precise interpretation of the rules. After all, the inspectors aren't trying to make teams fail—quite the opposite.

An additional layer of complexity is what the GDC thinks. As has been demonstrated repeatedly over the past decade or so, the Q&A operates on a different level to inspectors and teams. I'd venture to say it's a less practical level, and frequently a less creative level. Oftentimes a Q&A response will presuppose limitations that aren't logically required by the rules. Nevertheless, the inspectors need to balance what the Q&A is saying with what their understanding of the rules' demands. (When those conflict, there's an ethical decision that may involve equitable remedies outside of what the Q&A explicitly instructs.) I raise this issue, because what I say here (generally) represents my opinion in a vacuum, and not necessarily what I would rule in a competition setting where other factors (beyond the rules) are at work.

Originally Posted by anthonyttu

To preform (my understanding) what your trying to accomplish without breaking any rules or even flirting with any of them. You might look into pneumatic clutches. If your not using any pneumatic's anywhere else on the robot it might not be a good solution for your problem. Just an idea.

[R68] and [R71] would prohibit pneumatic clutches.