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Comments by Jan
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Understanding battery capacity: Ah is not A
- 28 August 2020Hi, Dave.
Sorry to hear about your golf cart. Unfortunately, your problem sounds like it doesn't have anything to do with the topic of this post and is instead just about troubleshooting the details of your control board, so I cannot help you with that. If you cannot get any information about your particular board, the main general advice I have is to try to get your hands on a thermal imager (they're getting cheaper and more ubiquitous all the time) and look for parts that heat up over those 1.5 hours of operation.
- Jan
Understanding battery capacity: Ah is not A
- 24 August 2020Jason,
I think you should just use one of those portable power banks (or "portable chargers" or "external phone battery pack") that already has USB ports built into it. There are so many sizes available and basic ones are so cheap now ($20 or less). Regarding the battery chemistries, sure, the secondary battery can be a different type than your main one as long as the electronics in between do the right thing.
- Jan
Understanding battery capacity: Ah is not A
- 28 July 2020Hi, 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
- 30 June 2020Hello,
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
- 15 June 2020Hello, 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
- 15 June 2020Hi, 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
- 14 June 2020Hi, 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
- 14 June 2020Kumar,
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
- 20 May 2020Hi, 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
- 20 May 2020Hi, 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