• ### Understanding battery capacity: Ah is not A

- 18 June 2012

Hello.

Your basic math is right, but keep in mind that capacity depends on discharge rate, so depending on the battery and how it's rated, it might not necessarily give you the 4320 mAh if you discharge it at 4.3 A. We do not carry any packs with that high of a capacity, but that's in the range of what you would get with "C" sized NiMH cells. You should be able to find receiver or servo packs with that kind of capacity at a hobby store (a quick search at Tower Hobbies led to http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXVTG1&P=7 ; at first glance, it might be what you're looking for). You could also consider lead-acid batteries; they will be bulkier, but they will probably be cheaper and easier to find in capacities exceeding 4Ah.

- Jan

• ### Three and a half months to plug in our machines legally

- 29 May 2012

Pete,

I am not suggesting that "qualified and accountable" people should not be involved. However, I think that government should not have a monopoly on safety standards and that the existing government monopoly leads to sub-optimal results (just look at the post above yours for an example). For instance, we could have facilities rated by some private company, and employees could choose whether to work in a place that was not rated or had a lower rating than they were comfortable with. Your insurance example shows yet another way the private market incentivizes safety. (And doesn't your suggestion of going to the insurance company indicate that you think the private company might have been more effective than the government?)

- Jan

• ### Three and a half months to plug in our machines legally

- 29 May 2012

Daniel,

Thanks for that perspective. I am generally in favor of leaving room for discretion, but that leads to more room for abuse because of the government's monopoly. If we instead had private inspections (which the county basically deferred to, anyway), there would be a little more room for alternatives if one particular inspector were being unreasonable.

- Jan

• ### Understanding battery capacity: Ah is not A

- 29 May 2012

The discharge rate could be an issue, so that's one reason going with 15Ah is probably better. However, the higher capacity battery could be an issue for the charger, depending on how that works. But 14 is pretty close to 15, so I would just go with the 15Ah. I would be very surprised if the 12Ah didn't work, though, so if that somehow fits better or is much cheaper, it should be fine (don't forget the 15 will give you 25% more run time than the 12).

- Jan

• ### Understanding battery capacity: Ah is not A

- 27 March 2012

Hi.

Most NiMH chemistries will probably tolerate at least a few C discharge rate, so an AA should be able to deliver at least 5A, which is plenty for the motor you're describing.

I have no idea what you're asking with this solar stuff, probably because you have little idea. Among your likely confusions: weight is not at all enough to tell us how much power you need, and getting more current available in your batteries is not going to force more current into your motor.

You should not be putting batteries in parallel unless you really know what you are doing, which in this case you do not.

Maximum, optimal, and safe discharge rates are completely separate. Any maximum rating better still be safe, and there will be a wide range of safe discharge rates. Optimal in terms of energy delivered will probably be around a few mA over a month, maximum could be 20A for a few minutes.

- Jan

• ### RC servo speed control

- 19 March 2012

Have you read (and understood) these servo control posts at all? If you are serious about your question, please provide a little more detail about what you are trying to do.

- Jan

• ### Advanced hobby servo control using only a timer and interrupts

- 2 February 2012

Yes, the time between pulses will not be perfectly constant, but that does not matter. I think I wrote quite a bit about that in the earlier posts.

- Jan

• ### Introduction to Jan's blog

- 25 January 2012

Dan,

Thanks for the feedback. It looks like you are aware that this is not the most appropriate avenue for this discussion, so you might want to think about what prompted you to post here before trying to contact us some more conventional way. You do bring up two subjects that I think are worth discussing publicly.

First and most directly addressing your comment, you got quoted a little over $500 for over 2500 identical little parts. A laser cutter is not necessarily going to be the most cost-effective way to do that kind of job, and if you have a better way of doing it, great: do it that better way. It's a similar situation with the competing quote: I don't think we promise being the lowest-cost option, but you might not be getting an apples-to-apples comparison since there are other factors like turn time, quality, support, etc. I'm not saying the cheaper options are necessarily going to turn out worse: I might have done your job for half or less back when I was running a laser out of my house. Still, a lot of your ire seems to be stemming from your disbelief about it taking four hours, and that does not sound that off to me. Second and more troubling is your resorting to complaining about greed, which seems all too popular lately. There's some rate at which things are worth it for us to do, and if that rate does not make sense for your application, don't go for it. There are probably things that you would not do for$100 but that you would do for \$1,000; does that make you greedy (in some bad way)? You say, "Might as well get them all cut, right?"; isn't that the same greediness? It's fine for you to come back to us with your other quotes to make sure there wasn't some miscommunication about your requirements or to try to negotiate a better price, but it's not appropriate or helpful to stoop to that kind of name-calling. Also, you should want to work and interact with competent people, for whom "greedy" probably isn't a particularly meaningful word.

- Jan

• ### RC servo speed control

- 10 January 2012

Hi.

The Maestros should give very good, smooth outputs, so the jerkiness is probably because of the servo you're using or the load you have on it. You're probably effectively getting a situation like the one in the last two diagrams, where the commanded position is gradually changing but the servo responds in jerks either because it isn't very good or because you have so much load on it that it can't move until the error is quite big. Can you put the same servo setup on an RC receiver and slowly move the controls on your transmitter?

- Jan

• ### November 2011 update: new building, new machines

- 4 January 2012

I want my office near Pololu Valley! We have customers on the Big Island, so it might be possible to see some of our products in action there (I remember hearing some talk of a robot club in Waimea a while ago, but I don't know what came of that). I don't think we have any distributors in Hawaii.

- Jan