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Comments by Jan
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Understanding battery capacity: Ah is not A
- 26 February 2018Hi, David.
Did you read the main post? It looks like you did not get the point of the amp vs. amp-hour distinction. (Or maybe it's just a typo in what you posted for your battery spec.)
In any case, if the battery is lasting a week, it's probably good enough. The main problem is that you are trying to use more energy in your lights overnight than you collect during the day. If you want to use 18W for eight hours and you have only 4 hours to collect that, you would need at least 36W. That would be at 100% efficiency, which for sure you will not have, and for the whole time, not just when you get the most direct sunlight. You probably need at least five times your current solar panel capacity.
- Jan
How I picked our new machines (and what they mean for you!)
- 14 February 2018Thanks. The bottom-side solder does become liquid again when the board goes through the oven a second time, but the surface tension of the solder keeps the components from falling off. What components we put on the side that goes through twice is something we consider when designing a board since something really heavy could fall off, and some components are better not to put through the oven twice. I don't think the solder joint quality is meaningfully affected by the second reflow cycle.
- Jan
Continuous-rotation servos and multi-turn servos
- 5 February 2018Hi, John.
Either of those routes will probably work, and it doesn't sound very expensive to try. 5k-50k is probably ok for the pot resistance. Let us know how it turns out!
- Jan
New adjustable voltage regulators with multi-turn fine adjustment
- 8 January 2018Thanks for the feedback. That higher output range you are asking for is not feasible on this particular design. Do you need the 3-16V input range in the same device, or are you wanting the higher output voltage for an application where the input voltage range would be smaller? (I'm asking because it's much easier to make just a step-up converter for low input voltage applications, and the step down/step up (or even straight step down) functionality would be easier to achieve if it did not have to operate at so low of a voltage.)
- Jan
Understanding battery capacity: Ah is not A
- 18 December 2017Hi, Cindy.
Your math generally seems right, though the "56 mA per use" is not correct; it's that times the two minutes to get back to units for total capacity. But the 56 mA is probably a more useful figure, as long as you realize it's not "per use" but the average rate over the two minutes. Maybe the motor only runs for 10% of that, and the remaining time the current is negligible, so the peak current draw might be over half an amp but only for ten seconds.
It sounds like the 5V, 1A adapter will likely be sufficient. In general, it's fine to use a bigger adapter since it's not going to force the currrent into your system.
- Jan
Free shipping, phase two: lots more free shipping
- 1 November 2017Hi, Dave.
If you meet us half way, you can get in on the free shipping! Hawaii has other benefits, too.
I know it's not the same as free shipping, but our international shipping rates are going down, and we keep working on getting them lower. Please also support your local distributors, and maybe bug them for free shipping!
- Jan
Understanding battery capacity: Ah is not A
- 18 October 2017Hi,
Your initial calculations seem right, except for the last one being a bit off: for 8 of those D cells I get 17*8*1.5=204; divide that by 4.8 and I get 42.5, not 43.75. Maybe you were approximating that 17 is basically half of 35 since 43.75 is half of the earlier 87.5.
For the last part, you can be pretty sure about the battery side. If you have 2Ah * 1.2V * 3 = 7.2Wh and you're getting many hours out of it, you can be sure the load is actually less than 3.6W. Maybe that's some conservative upper limit, perhaps at a higher voltage like 4.8V (1.6V per cell), and the actual consumption might be half that at 3.5V and drop even more as the battery voltage goes down. If there isn't some fancy flashing pattern, it should be really easy to just measure the current at different voltages.
- Jan
Understanding battery capacity: Ah is not A
- 11 October 2017Hi.
For the first question, yeah, your power should basically scale with the number of motors. Keep in mind that you won't necessarily get to use that extra power the way you want to, which brings us to your second question, where the answer totally depends on your system. Even if you have a system in which your output power is constrained to be the exact same in both scenarios, your system efficiencies will not be the same, and more importantly, the motors would not be operating at the same efficiency points. Back to real life systems, if you have more power available, your robot will move faster at top speed or accelerate more quickly, so your output power is unlikely to be constrained to the same value in both situations.
- Jan
Understanding battery capacity: Ah is not A
- 22 September 2017Hello.
If you understand the system you are putting the battery into, you should be able to tell if anything would be affected badly. The 10 Ah battery should last about four times as long as the 2.5 Ah battery, and if you don't change anything, charging should take about four times as long. If you are putting the battery into a system you do not understand or control, things could be more complicated, depending on how smart or helpful your device is. For instance, you might be fine waiting 20 hours instead of five hours for charging, but your device might have a timeout after six hours or it might think there is a problem and stop working normally.
- Jan
Understanding battery capacity: Ah is not A
- 30 August 2017Hello, Don.
You generally cannot force a current out of a battery and into something. If you have a load that wants to use 3A when you connect it to 12V, the battery should be capable of delivering that.
- Jan