Comments by Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 28 July 2020

    Hi, Andrew.

    The NiCd pack will likely give you more power or speed because that is a question about how fast you can get the energy out of the battery, not about how much is in there.

    - Jan

  • 37D gearmotors: helical pinion gear, new 150:1 gear ratio, and performance graphs

    37D gearmotors: helical pinion gear, new 150:1 gear ratio, and performance graphs

    - 30 June 2020

    Hello,

    The temperature range is -10 to 60 degrees C. They are not ISO 9001 certified (or certified to any other standard besides RoHS where indicated).

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 15 June 2020

    Hello, Sakar.

    Just do the math:

    3.7 V * 1 Ah = 3.7 Wh
    4 * 1.5 V * 2 Ah = 12 Wh

    So the alkalines should last over 3x as long, provided you can do something useful with that extra energy. You could still make the alkalines last less long; in one extreme example, if the pump can run on the approximately 3V you would give it from the Li-ion source, giving it 6V from the four alkalines in series might cause the pump to burn out in less than the 5 hours it should run on the lithium battery.

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 15 June 2020

    Hi, Matt.

    Solar cells can be weird (you can look at https://en.wikipedia.org/wiki/Maximum_power_point_tracking to get a bit of an idea), and there's a lot of details about your setup missing (notably, there are no voltages anywhere!). From the information provided and depending on how you wire things, the possible outcomes could range from the LEDs not turning on as brightly as you expect to burning out your LEDs (possibly not instantly, but maybe significantly shortening their lifetime if you let the current through them be too high).

    However, 20mA is not that much, so I suspect you'll be fine. You should look at power, though. If your LEDs are red LEDs at 1.8 V or so, you're using half as much power for the same current as a white LED at 3.6V. LEDs also need something limiting the current because they'll just burn out if you give them too much voltage. If we go with the 3.6V case, your three LEDs will use a total of 3.6 * 0.02 * 3 = 0.216W. That doesn't count any converter and LED driver efficiency, where you could easily lose half your power. If your solar cell outputs 150 mA, you're probably fine if it can do that at 3V (therefore outputting 0.45W), and not so fine if the output voltage is only 1V at 150mA (outputing 0.15W).

    - Jan

  • Rethinking open source in the context of the coronavirus pandemic

    Rethinking open source in the context of the coronavirus pandemic

    - 14 June 2020

    Hi, Chris,

    Thanks for sharing your experience and perspective. It's good to keep in mind that I probably hear about open-source hardware more from the few people promoting it than from people like you who have actually gone out and tried it on a big scale. It sounds like you found a balance, though (on the software side), and I wonder if there still might be (profitable) room for some OSHW products at Pololu. One advantage we have is that we have a broad array of products, so we can try it with a few of them to see how it goes.

    - Jan

  • COVID-19 impact update: still hanging on after three weeks

    COVID-19 impact update: still hanging on after three weeks

    - 14 June 2020

    Kumar,

    Thank you so much for your generous support! It's hard to believe it has been more than two months since I wrote this post. Continued help from you and others after the immediate shock of the business shutdowns has faded is so crucial in making sure we can get through this. Just this past week I heard of two local businesses (not electronics related) that I have frequented over the years closing. It must be so devastating for the business owners and employees.

    We are working hard to ensure we make it. Thank you everyone who has continued to support us, through donations, continuing to do business with us, and cheering us on by telling us what we mean to you.

    - Jan

  • Rethinking open source in the context of the coronavirus pandemic

    Rethinking open source in the context of the coronavirus pandemic

    - 20 May 2020

    Hi, Tim.

    If you go to eBay or Amazon and search for "Pololu stepper driver", pretty much all the results are knock-offs.

    For another example, search for VNH5019. You'll see multiple examples of boards that have exactly our parts arrangement and label layout (i.e. it's not just about a functional solution to a problem).

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 20 May 2020

    Hi, Emmanuel.

    The charging time will depend on efficiencies we do not know. However, the capacity of the battery is 12V * 40Ah = 480Wh, so if you had perfect efficiency, you would need 3.2 hours to transfer that into the battery at 150W. If your system (including the charger, the battery, and the solar panel when connected to that particular charger and battery) had 50% efficiency, it would take about 6.4 hours to charge.

    - Jan

  • Understanding battery capacity: Ah is not A

    Understanding battery capacity: Ah is not A

    - 20 May 2020

    Hello, Ralo.

    Knowing the battery capacity is not enough to know how much power or current your device uses. If you can know for sure that the power consuption is steady, you can divide the 4.5Ah by how many hours the device runs to get an estimate. If it runs 2 hours, it draws 2.25A on average; if it lasts 15 minutes, it draws 18A on average.

    If it's something that uses power unevenly, though, it's hard to know. Many devices have a peak current consumption ten times or a hundred times what the average is, and your power adapter generally needs to be able to supply the peak to avoid malfunction of the device.

    - Jan

  • Rethinking open source in the context of the coronavirus pandemic

    Rethinking open source in the context of the coronavirus pandemic

    - 26 April 2020

    Hi, Dan!

    I hope you are doing well, and thanks for your comments.

    Yes, dealing with support for units from other sources would still take up our time, but I'm hoping that the balance would get better. As in, initially, keeping things closed might help prevent this problem. But once there are enough copies out there, anyway, we're getting the negative of extra support overhead without the positive of others possibly supporting our customers (or the more resourceful ones supporting themselves better, e.g. with questions like, which resistor is R3 in the schematic?). So, I just think the balance might be better for us now than it was eight years ago.

    Surely there are some benefits to manufacturing locally, and surely some people are more aware of them now. That does not mean global trade is not important or that it needs to be resisted via government intervention. I think there might be more people willing to voluntarily buy something from me for $4 that they might have ordered from China for $3. If I'm happy making that thing for $4, isn't that overall a good thing?

    Why would it be more sensible to solicit donations after a product is open?

    And on your last point, I'm not sure if you are making a distinction for "free software" vs. open source. The scope I am thinking about includes software (including firmware), electronics, and mechanical designs, and as far as details of licenses or implementation, I'm probably thinking about the equivalent of making the designs/projects/whatever public domain.

    - Jan

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