Converting 12v to 24v
 

We are planning on using an electromagnetic clutch to "freespin" a van door motor for our launching device. The only problem is the electromagnetic clutch from the vendor we are allowed to purchase through is a 24v device.

Is it legal to have a 12v to 24v converter?

Re: Converting 12v to 24v
 

If it's just a permanent magnet motor, on 12V it will simply run at half speed and have a lower stall torque. Will this be a problem? How much of the speed and torque performance of the device do you need?

Graham.

Re: Converting 12v to 24v
 

I don't think he is talking about a motor.. I'm guessing that the electromagnet will engage or disengage a clutch separate from the van door motor. I don't see anywhere that a converter is illegal, but just remember, the 12 volts will drop to about 7 volts sometimes, especially in pushing matches.

Re: Converting 12v to 24v
 

I don't see purchased electromagnetic clutch assemblies listed in [R48]. Is there a ruler somewhere else that makes this legal?

Re: Converting 12v to 24v
 

Perhaps this is this being used under the new rule which permits solenoids? If so, it must be no more than 10 watts.

Re: Converting 12v to 24v
 

Maybe, maybe not. Before investing too much effort on this, you might want GDC to clarify rule [R48]J with respect to this question.

Re: Converting 12v to 24v
 

I agree that you should ask in the Q&A if it is legal before preceding.

What is the the force the clutch is rated to transmit? If you don't need all of that force you may get enough force running it at 12v.

Re: Converting 12v to 24v
 

This question has come up before.

In 2005, the rules were different, and all electronic "motor[s], solenoid[s], pump[s] or other actuator[s]" were prohibited, other than the ones in the KOP. (This type of clutch is either a solenoid or other actuator.)

In 2010, the rules were more similar to 2012. In that case, the Q&A noted that if the clutch did not contain a prohibited actuator (and implicitly, did not violate any other rules), it would be allowable. In 2010, there was some unresolved discussion about whether the clutch contained a true solenoid, or merely some other type of electromagnetic actuator.

For 2012, [R48] provides a new complication, because it now says "The only motors and actuators permitted on 2012 FRC Robots include" instead of "Motors specifically permitted on 2010 FRC ROBOTS include". This means that a new restriction on actuators has been explicitly added for this year.

Therefore, if the clutch contains a solenoid, then that solenoid must meet the specifications from the rulebook for the clutch to be legal. If the clutch does not contain an appropriate solenoid (or other thing from [R48]), it's a prohibited actuator. (Of course, the device must also meet all other rules, particularly the ones dealing with custom circuits and power regulating devices for actuators.)

I think the rule is clear in its meaning, but not so clear in its intent. Why ban a device that was previously allowed, even as you allow solenoids for the first time in over 10 years (and possibly ever)? You might therefore want to raise it in the Q&A not for clarification, but with the intention of prompting FIRST to change the rule.

Re: Converting 12v to 24v
 

With respect to this issue, the converter is a custom circuit, and must therefore conform with [R47], which says that "[c]ustom circuits shall not directly alter the power pathways between the battery, PD Board, speed controllers, relays, motors, or other elements of the Robot control system (including the power pathways to other sensors or circuits)."

You might want to ask the Q&A whether a solenoid actuator is an other element of the robot control system, as enumerated in the rule. That will determine if your custom circuit can legally affect it.

Re: Converting 12v to 24v
 

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.

Re: Converting 12v to 24v
 

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

Re: Converting 12v to 24v
 

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.

Re: Converting 12v to 24v
 

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

Re: Converting 12v to 24v
 

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.

Re: Converting 12v to 24v
 

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:
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.

Re: Converting 12v to 24v
 

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).

Re: Converting 12v to 24v
 

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.)

Re: Converting 12v to 24v
 

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.

Re: Converting 12v to 24v
 

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.

Re: Converting 12v to 24v
 

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

Re: Converting 12v to 24v
 

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?

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>.

Re: Converting 12v to 24v
 

Tristan,
The above rule lists the only devices that could be used on the robot. There was no hidden or silent list of actuators that could be used. There is nothing that would be allowed if it wasn't on the list. There was no custom circuit that could be or act as an actuator. The list was the only actuators that you could use.

From the Q&A...
"Re: clutches
Posted by GDC at 01/21/2010 10:54:45 pm
There is no rule specifically prohibiting the use of clutch mechanisms on the ROBOT. However, these devices may not be used if they contain electric motors and/or servos different from, or in addition to, those in the KOP, solenoid actuators (per Rule <R53>) or pneumatic actuators (such devices are not explicitly permitted by Rule <R72>, and therefore violate Rule<R71>).

Simply put: if the device utilizes an electric solenoid to provide mechanical motion for the device, it cannot be used."

In addition to the above, the GDC also ruled that relays (solenoids with electrical contacts) other than Spikes could not be used on the robot even if fully contained in a custom circuit and meeting all other robot rules.

The only movement on the GDC's part that even comes close was to allow an electromagnet that holds something in place while energized and simply released it when the current was removed.

Re: Converting 12v to 24v
 

For 2012: "The only motors and actuators permitted on 2012 FRC Robots include...". This is exclusive with respect to motors and actuators.

For 2010: "Motors specifically permitted on 2010 FRC ROBOTS include..." and "Items specifically PROHIBITED from use on the ROBOT include...motors [not from the KOP or otherwise permitted]...[and] solenoid actuators". This is exclusive with respect to motors and solenoid actuators, but not exclusive with respect to actuators that are neither motors nor solenoids.

That non-exclusivity is the important fact. If the bell or clutch was not a solenoid or motor, then it would not have been prohibited in 2010. (And if it was a solenoid or illegal motor, it would have been prohibited.)

Since the 2012 rule is exclusive, it works the opposite way: if the bell or clutch is a solenoid, then it must meet the requirements for solenoid actuators. If it is not a solenoid actuator (or a legal motor), it is prohibited.

The rules provide no reason to believe that a device can't simultaneously be a custom circuit and an actuator. (Indeed, having both sets of constraints apply simultaneously is desirable...otherwise teams could use legal actuators without regard to the specific electrical conventions required of custom circuits.) Though admittedly the rules aren't clear about this, for 2012 there isn't really any reason why any motor couldn't be considered a custom circuit...there's no significant discrepancy between the motor requirements and custom circuit requirements. I doubt this is necessarily what FIRST intended, but at least it doesn't conflict.

I'm contending that it doesn't meet the definition of solenoid, and therefore doesn't conflict with the rule or the Q&A quoted above.

Solenoids would have been illegal in 2010 as you and the GDC stated.

Re: Converting 12v to 24v
 

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.

Re: Converting 12v to 24v
 

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.

Re: Converting 12v to 24v
 

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.

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

Re: Converting 12v to 24v
 

Look around the web and you find many definitions of solenoids. One thing that many have in common is that it's coil of wire than when energized creates a magnetic field that causes a linear motion. So yeah I'd say a magnetic clutch would fall under the solenoid rules and 10w at 12v is not going to create a enough force to transmit very much torque.

For our kicker for Breakaway we created a created a transmission based on the AM super shifter. Basically we built a custom case and left out the high idler gear. In the low gear position it transmits power and shift it into the "high" gear and it freewheels. Because it was under a lot of torque we had to shift it with a lever arm to generate enough force.

Re: Converting 12v to 24v
 

Tristan,
You are going way out on a limb here.
"If the bell or clutch was not a solenoid or motor, then it would not have been prohibited in 2010." The bell is a solenoid and so is the clutch you show. I have worked on a couple of hundred of these air conditioning clutches over the years. The clutch plate is pulled by the magnetic field set up by the electric current. The pull mates a frictional plate with a metallic plate to lock the pulley to the drive shaft of the compressor. If you stick your finger between the plates when you energize the coil it will get pinched.

"This is exclusive with respect to motors and solenoid actuators, but not exclusive with respect to actuators that are neither motors nor solenoids." What actuator is neither a solenoid or a motor or a pneumatic part?

"Since the 2012 rule is exclusive, it works the opposite way: if the bell or clutch is a solenoid, then it must meet the requirements for solenoid actuators. If it is not a solenoid actuator (or a legal motor), it is prohibited." Exactly!

"Though admittedly the rules aren't clear about this, for 2012 there isn't really any reason why any motor couldn't be considered a custom circuit...there's no significant discrepancy between the motor requirements and custom circuit requirements. I doubt this is necessarily what FIRST intended, but at least it doesn't conflict." How can you draw this conclusion from both the motor list that you state is an exclusive list (excludes all motors not on the list) and from the custom circuit rules which prevent any custom circuit from direct control of a motor?

[R47]
Custom circuits shall not directly alter the power pathways between the battery, PD Board, speed controllers, relays, motors, or other elements of the Robot control system (including the power pathways to other sensors or circuits).

So what exactly are you thinking could appear on an FRC robot that is neither a solenoid nor a motor nor a pneumatic part, that would be in your mind, a legal actuator?

Re: Converting 12v to 24v
 

I don't see the loop hole but I'm not the GDC. Many years ago we prototyped a friction clutch that only used a Hitec servo to hold. It can be done. If you have air on the bot a friction clutch is easier. A little 3/4" piston is all that is needed.
With out a clear ruling from the GDC find another way. If this is for a catapult, there was a video earlier that showed a team using a eccentric cam to operate the catapult.

Re: Converting 12v to 24v
 

Is a speaker a solenoid?

Not all electromagnets are solenoids. I looked at a few definitions of "solenoid" just now, and the common feature was that they all either moved an armature inside the coil, or moved a coil between permanent magnets. From what I can see, neither the bell nor the magnetic clutch fits that category.

What matters in the end is not what I think "solenoid" means, or what you think it means, but what the GDC thinks it means. Until someone asks and gets a clear answer, I'm personally going to be conservative and eschew electromagnets in general unless they satisfy the motor or electric solenoid actuator rules.

Re: Converting 12v to 24v
 

Alan,
A speaker is a solenoid and often it is referred to as such in technical literature. In relation to a what we normally think of as a solenoid, the coil moves in a speaker instead of remaining stationary as in a common solenoid.
As I stated much earlier, a solenoid by definition moves something when an electric current flows. The bell does exactly that.

Re: Converting 12v to 24v
 

Sounds like a speaker to me. :) But speakers would be prohibited under the no noise maker rule?

Read 2012 rule 48. If clutch is operated by a magnetic coil, you should be arguing that it is a solenoid otherwise you cannot use it unless it is powered by an allowed servo or motor.

While I generally do like stretching definitions, what GDC it trying to do is fairly clear. They trying to allow small magnetic actuators and at the same time keep the rules short.

Re: Converting 12v to 24v
 

And the GDC has it!

I just got a response from the official Q&A System.

Q. We want to use an electromagnetic clutch on our robot. The clutch is a 24v component. 1)Is it legal to have a power converter to convert 12v to 24v 2) Are electromagnetic clutches a legal component since they use no actuator?
A. 1) Yes, provided all other Robot Rules are met. 2) There are no Rules specifically prohibiting the use of clutch mechanisms on the Robot. However, these devices may not be used if they contain electric motors and/or servos different from, or in addition to, those permitted in the Robot Rules. Simply put: if the device utilizes an electric solenoid to provide mechanical motion for the device, that solenoid must meet the requirements of Rule [R48-J].

The only problem I see is that in order to use a smaller electromagnetic clutch it must be 24v. There is nothing against having a 12v to 24v converter as long as it follows all other robot rules. But R48-J states that solenoid must 10 watts continuous duty at 12v.

Re: Converting 12v to 24v
 

I don't dispute that it moves as you describe. We only really differ on the definition of a solenoid (and solenoid actuator).

I'm saying that we need to be discerning about what is a solenoid, lest low-quality solenoids like loops of wire be dragged into the discussion (an outcome nobody wants or believes should exist). I'm presuming that the uniformity of the magnetic field within the core is the distinguishing characteristic of a solenoid. Additionally, even in the presence of a pretty good solenoid, I'm asserting that it's not a solenoid actuator unless the device is using the characteristics of a solenoid (rather than an electromagnet in general) to do its work.

That leads to the distinction I described between solenoid actuators, and electromagnetic actuators (a broad class of devices that includes solenoid actuators and motors).

According to my contention, the bell, and maybe the clutch.

If you really want to get creative, I guess an electric actuator that is none of those things might take the form of a bimetal strip combined with a resistive heating element. When you raise its temperature, it bends to a specified position.

Actually, as we discussed earlier, [R48] certainly applies to (at least some kinds of) electromagnetic acutators, and certainly does not apply to pneumatic actuators (because if it did, all pneumatics would be illegal, for lack of mention in [R48]). But does it apply to electroresistive actuators? (Or piezoelectric actuators, or static electric actuators, if such things even exist?)

Also, we can't just apply [R48] to all actuators not explicitly permitted elsewhere (like we might be tempted to do, to get around the pneumatic actuator problem). Then purely mechanical actuators (like a flyball governor) would be prohibited. Nobody wants that—and more importantly, it would be a non-obvious and perhaps even unfair restriction to enforce at inspection.

That's the rule I had in mind—you can't alter the power pathway between the device and the power source, but you can alter the pathway inside the device.

If "between" was meant to include the device itself, it would be impossible to make custom circuits that draw power from the robot. Normally it's moot, because you can't really alter motors legally.

But there's no actual conflict between the motor/actuator and custom circuit rules that prevents a device from simultaneously satisfying the requirements for both.

I say there's confusion, only because I don't think that's what the GDC intended, and it may be worth asking them "if a device is (or contains) a motor or other electric actuator, does that exclude it from being a custom circuit".