Callipygous

Id probably prototype with aluminum and 3d prints, and if you find you really need the lighter weight switch to carbon fiber once you've ironed out the kinks.

I don't know about robot design, but it seems like this would depend entirely on your project's limitations. Mountain bikers will tell me that carbon wheels are totally worth it, but they are not in my budget and I don't ride hard enough to care about the difference. Its worth it for them, but not for me. Does your budget support the difference in cost? Can your robot tolerate slower arms, or bigger motors to move heavier arms?

I'm down to experiment with any such configurations. Right now I am working with the usual linear arrangement and struggling to get enough force out of it. I can tell that its working in that it will pull a paperclip sideways if I dangle it like a pendulum, but it is not generating enough force for me to even feel it. So I think the first hurdle is going to be figuring out what my minimum power supply is going to have to be. Since I want it to be as small as possible, that means figuring out how to design the most efficient coil. I was thinking last night with regard to wire size and number of coils. My current solar panel generates 3.2v and will output about 0.2mA. I think this means my coil will need about 16000ohms before my current is restricted by the coil rather than the solar panels output. Since hooking up the coil does not seem to decrease the current vs a short circuit, I think this means I can afford to switch to a smaller wire size to get more coils without losses due to resistance. Can anyone confirm if that logic checks out? I am aware that this solar panel may be entirely too small to serve this purpose. I would like focus on the physics and solenoid design for now.

I am trying to fit a solenoid into a greeting card to animate parts of it. I would like it to run on the sorts of power sources that could also be squeezed into a greeting card, so coin cell batteries, or very thin flexible solar panels. To that end, I have been trying to learn about how to optimize the design of a solenoid to get the most bang for my wattage, and mostly running into more and more complications. I am hoping someone can help me understand sort of practical rules of thumb for solenoid design. For example, in trying to keep my solenoid very small in diameter, I wondered if I could make up for it by making it longer. If I understand correctly, the equation for the maximum pull force has number of coils in the numerator and length of the solenoid in the denominator, so making a longer solenoid would be a wash. Right now my current doesn't drop if I measure just the solar panel, vs the solar panel with my solenoid in the loop, so I wondered if maybe I should be using even thinner wire to fit more coils in. Then I found a source saying that as you decrease wire size you fit more coils in but also increase the resistance and decrease the current, so it ends up being a wash. Pulling force is proportional to the number of coils, but also proportional the cross sectional area of the armature. So if I'm limited to 1/4" or so diameter, how do I balance armature size vs space available for more layers on the coil? Is that a wash too? The only thing I've found that seems sorta solid is that I should wrap the whole thing in backing iron, but I cant seem to find an answer about how to size that either. Is iron foil sufficient, or do I really need more like 1/8" of iron to have an impact? Where's the point of diminishing returns?

I mostly agree with your math. The part I wonder about is whether the batteries have a fixed output, or a recommended maximum output. What I do know is that the project has worked successfully for reasonable periods of time. The latch is activated for 2 seconds at a time. I don't know if that qualifies as a sustained load, or if they really mean "don't draw that much for 2 hours" The link from my original order no longer works, but the latch is basically identical to this. That claims a draw of .43 amps, which is more than your calculation says my batteries should be okay with. So again, I don't know if it's really a fixed output or a maximum recommended, but I do know that it worked, repeatedly, and for a period of at least a few weeks. The latch at least appears to be ok with the available current. The issue seems to be with consistently providing that current. maybe some part of this set up damaged the converter? Actually, I have two of those battery packs wired up in parallel, so really the peak output is doubled. So the latch is probably fine, though I'm not sure how much the Pi is adding onto that. Still not sure if a 2 second use should be counted against peak or sustained. Ah, now I see the miscommunication. Those are both too large to meet my requirements. This entire project lives in a space that is about 4 wide x 3 deep x 4 high. And the front is slanted, so at the top its only about 2 inches deep. after the batteries, pi, and other components I really need the dc converter for the latch to fit into about 1x2x2. It also runs off batteries, so a PC power supply designed to plug into the wall doesn't fit the bill. I need something to step 3 volts up to 12 volts.

I have been trying to figure this out. It looks like there are some options that are basically what I'm using, which is variable input, adjustable output in the ~3-30v range. Then there are some other ones that seem like they might be easier to use and more reliable, because they aren't adjustable, they just put out 12v. So far I haven't figured out how to consistently find and filter those. This is the closest I have found so far. The downside is they talk about current more like 50mA, not the 1-2 amps I think my latch probably needs. You have any hints for how to specify the non-adjustable types? Does the one I linked even seem like what you were referring to?

no desire to complicate things, just lack the experience to know about that and the vocabulary to find it.

I made a project involving voice recognition on a raspberry pi so you can speak a password to open a box. Long story short, my DC-DC step up converter to power the latch seems to be super unreliable. I am wondering if some of my trouble is related to how I have it wired up and if someone could suggest a better approach. I have 2 battery packs (https://www.adafruit.com/product/354) wired in parallel. Those are powered off a charger (https://www.adafruit.com/product/390) So output of this board, and the two batteries, are connected to the main positive and negative lines at the edge of my PCB. Attached to those lines I have a boost converter (https://www.adafruit.com/product/2030) which powers my raspberry pi. Also attached to the main lines, I have an adjustable boost converter (https://www.amazon.com/gp/product/B01MS3IAVL/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1) the positive on the positive line, the negative comes back to the collector of a TIP 120 (https://cdn-shop.adafruit.com/datasheets/TIP120.pdf) the emitter goes to the negative line on the PCB. The base is connected via a resistor to GPIO on my raspberry pi. I had it all sorted out and working about 2 weeks ago, and then it just stopped. I have had problems numerous times when I came back to the project and the output voltage of my converter had drifted from the desired 12V. So when it stopped working I opened the box up and checked on it, it was putting out 5 volts and wouldn't respond to adjustments on the potentiometer. I have been troubleshooting all weekend, but just now I tried wiring it directly to the battery lines and it works as expected. Is something about my setup throwing it off? Do I just have a cheap, unreliable boost converter? Interestingly, on my original order it says the input range is 3-32v, but now the link I provided says 5-32v. Could my problem be related to low input voltage?

i hate to bring seriousness to an obvious joke, but often times the confusion comes in not understanding how the register works. when they first put you in front of the register they tell you what buttons do what, and thats it. after that you just do your best to keep up with the customers orders without making some stupid mistake that is going to get them coming back complaining to your manager about the tomato on their burger. there are certain parts of the transaction where, to undo it, you need to call over a manager and have them use a code to let you redo the transaction. so if she already typed in the amount you gave her and you hand her more money, and shes new to using the register, she may just be confused as to exactly what needs to be done as far as the register is concerned, not what your change should be. if she had time to think about it, shed realize the register doesnt need to know what exactly went in and out, as long as the right amount of money ends up in there, but when your first thrown into the job you dont bother to think about that, you just try to remember all the stupid unlabeled buttons. please, be nice to the ordertakers. i believe i owe you a joke now. there was an altercation between 2 turtles and a snail. the police were talking to the snail about what happened. the snail said "well officer... it all happened so fast."

my grandfather frequently sends me emails, most of which are highly inappropriate, but this one isn't and i felt compelled to share it: Far away in the tropical waters of the Caribbean, two prawns were swimming around in the sea - one called Justin & the other called Christian. The prawns were constantly being harassed & threatened by sharks that inhabited the area. Finally one day Justin said to Christian,"I'm fed up with being a prawn, I wish I was a shark, then I wouldn't have any worries about being eaten." A large mysterious cod appeared & said, "Your wish is granted" & lo & behold, Justin turned into a shark. Horrified, Christian immediately swam away, afraid of being eaten by his old mate. Time passed (as it invariably does) & Justin found life as a shark boring & lonely. All his old mates simply swam away whenever he came close to them. Justin didn't realise that his new menacing appearance was the cause of his sad plight. While swimming alone one day he saw the mysterious cod again & he thought perhaps the mysterious fish could change him back into a prawn. He approached the cod & begged to be changed back, & lo & behold, he found himself turned back into a prawn. With tears of joy in his tiny little eyes Justin swam back to his friends & bought them all a cocktail. (The punch line does not involve a prawn cocktail - it's much worse). Looking around the gathering at the reef he realised he couldn't see his old pal. "Where's Christian?" he asked. "He's at home, still distraught that his best friend changed sides to the enemy & became a shark" came the reply. Eager to put things right again & end the mutual pain & torture, he set off to Christian's abode. As he opened the coral gate memories came flooding back. He banged on the door & shouted, "It's me, Justin, your old friend, come out & see me again." Christian replied,"No way man, you'll eat me. You're now a shark, the enemy, & I'll not be tricked into being your dinner." Justin cried back "No, I'm not. That was the old me. I've changed....... "I've found Cod. I'm a Prawn again Christian"

Mrs Tilly loves the roof but not the ceiling. i like this puzzle... its deep, but not profound.

it might help if you defined chav and innit.

this one might be US specific. im not sure how wide their reputation has spread... how do you know if theres a marine at a party? hell tell you.

you are a kid. genius is overrated (literally). find something worth while to brag about.