7 ms·

Building a Handheld PC

202 points by lo2y 3y ago

smilespray 3y ago
It says the charging voltage is 8.2V, which is double the usual charging voltage for lithium cells. Is it really safe to connect two 18650 cells in series like this? I've read that you should manage each cell individually to reduce wear and/or risk of fire.
- deleted 3y ago
  [deleted]
- RF_Savage 3y ago
  If the cells are matched it is less of a problem. But 2S battery management boards with additional features like low voltage cutoff and current limits are only a few euros in single quantities, so I see no reason not to use them.
- RobotToaster 3y ago
  Looks like he's using a BMS with a centre tap to balance the cells.
  - smilespray 3y ago
    I looked up the module on AliExpress: https://www.aliexpress.com/i/1005004814091297.html https://www.aliexpress.com/i/1005004814091297.html Anybody care to have a look and comment?
    - RobotToaster 3y ago
      I could only find a datasheet for the chip in Chinese, but from what I could get through google translate it looks like it can balance two or three cells in series.
simonjgreen 3y ago
This is a fantastic demonstration of how accessible all this stuff is these days. Polish used to be the let down on DIY projects like this but 3D printers (for the case) have really moved the needle when it comes to high quality prototyping. I know this has been the state of things for nearly a decade now, but it still amazes me. Raspberry Pi, Arduino, 3D Printers, and the open source hardware community, will mark a paradigm shift in prototyping accessibility in the history books.
- amelius 3y ago
  It's super cool, but at the same time for many folks an iPad Mini with/without external keyboard would be a more adequate solution considering processing power.
  - detrites 3y ago
    I don't think so. It could be very tricky to modify an iPad mini sufficiently to become a piece of custom hardware that you're prototyping. Except in the case you were prototyping an iPad mini itself, which of course would be child's play.
  - jstanley 3y ago
    This sort of comment is actually a rather obscure compliment. If you make something that's obviously shoddy, nobody confuses it for a serious product. Nobody is telling grandma that her knitting isn't as practical as a waterproof jacket from J. Random Outdoorswear Company. Nobody is telling the electronics newbie that a blinking LED isn't actually of any use to anyone. Everybody has nothing but positive encouragement. But if you start to make actually really good stuff, requiring an enormous amount of skill and experience, you instead get "cool, but actually not quite as good as the nearest commercial competitor". If you're so good at your hobby that people are comparing you to the literal state of the art, you're doing something right.
    - johnwalkr 3y ago
      I love this comment! As someone who works in hardware in a demanding industry, although not in consumer electronics, this example obviously has a long way to go to compete with a real product, because you have big hurdles in moving to integrated designs instead of integrating devkits, and in moving to manufacturability at scale. I don't think that's even the intent but I can see it at least as a niche product. I only say this to set up the next statement. This thing is great to show vision and usability, and I'm more excited by this than a lot of dead-end things I've seen presented as a bunch of requirements and if you're lucky, renderings made by a lot more than one person and 3 weeks. And think about the software world, it's understood that framework X makes a great example but needs to be replaced by microservices Y, and also understood that people exist to make that happen. It's not like grandma's knitting, but it could be something like MVP software to get a cofounder and an angel investor.
subtlemuffins 3y ago
https://www.clockworkpi.com/uconsole https://www.clockworkpi.com/uconsole
- JKCalhoun 3y ago
  Those are cool.
5mv2 3y ago
Have you thought of doing the same with an e-ink screen? I would find it awesome to get work done while in nature.
- loxias 3y ago
  It's just as awesome as you think. Sadly, those projects always end up getting cancelled.
_Microft 3y ago
Since PCB manufacturing has become super cheap, they could consider having a custom L- or U-shaped custom PCB around the battery box that serves no other purpose than routing signals and power to where they are needed and solder the different boards directly onto that. That would also allow to place supports for this large PCB where they are convenient instead of having to separately mount each of these small PCBs to the case. With less cables in the way, they might get better airflow in the case as well. Edit: I guesstimated the size and think that they could get five pieces of such a board for less than 20€, including delivery.
sgtnoodle 3y ago
I hope they used something other than PLA. I've made some really nice enclosures that warped over time from heat.
bullen 3y ago
What SoC is this using? For the life of me I can't find it in the article? Edit: ok it's a CM4? on the back of the display... For others searching for the secret sauce: BigTreeTech Pad 5

202 points by lo2y 3y ago

It says the charging voltage is 8.2V, which is double the usual charging voltage for lithium cells. Is it really safe to connect two 18650 cells in series like this? I've read that you should manage each cell individually to reduce wear and/or risk of fire.

deleted 3y ago
[deleted]
RF_Savage 3y ago
If the cells are matched it is less of a problem. But 2S battery management boards with additional features like low voltage cutoff and current limits are only a few euros in single quantities, so I see no reason not to use them.
RobotToaster 3y ago
Looks like he's using a BMS with a centre tap to balance the cells.
- smilespray 3y ago
  I looked up the module on AliExpress: https://www.aliexpress.com/i/1005004814091297.html https://www.aliexpress.com/i/1005004814091297.html Anybody care to have a look and comment?
  - RobotToaster 3y ago
    I could only find a datasheet for the chip in Chinese, but from what I could get through google translate it looks like it can balance two or three cells in series.

simonjgreen 3y ago

This is a fantastic demonstration of how accessible all this stuff is these days. Polish used to be the let down on DIY projects like this but 3D printers (for the case) have really moved the needle when it comes to high quality prototyping. I know this has been the state of things for nearly a decade now, but it still amazes me. Raspberry Pi, Arduino, 3D Printers, and the open source hardware community, will mark a paradigm shift in prototyping accessibility in the history books.

amelius 3y ago
It's super cool, but at the same time for many folks an iPad Mini with/without external keyboard would be a more adequate solution considering processing power.
- detrites 3y ago
  I don't think so. It could be very tricky to modify an iPad mini sufficiently to become a piece of custom hardware that you're prototyping. Except in the case you were prototyping an iPad mini itself, which of course would be child's play.
- jstanley 3y ago
  This sort of comment is actually a rather obscure compliment. If you make something that's obviously shoddy, nobody confuses it for a serious product. Nobody is telling grandma that her knitting isn't as practical as a waterproof jacket from J. Random Outdoorswear Company. Nobody is telling the electronics newbie that a blinking LED isn't actually of any use to anyone. Everybody has nothing but positive encouragement. But if you start to make actually really good stuff, requiring an enormous amount of skill and experience, you instead get "cool, but actually not quite as good as the nearest commercial competitor". If you're so good at your hobby that people are comparing you to the literal state of the art, you're doing something right.
  - johnwalkr 3y ago
    I love this comment! As someone who works in hardware in a demanding industry, although not in consumer electronics, this example obviously has a long way to go to compete with a real product, because you have big hurdles in moving to integrated designs instead of integrating devkits, and in moving to manufacturability at scale. I don't think that's even the intent but I can see it at least as a niche product. I only say this to set up the next statement. This thing is great to show vision and usability, and I'm more excited by this than a lot of dead-end things I've seen presented as a bunch of requirements and if you're lucky, renderings made by a lot more than one person and 3 weeks. And think about the software world, it's understood that framework X makes a great example but needs to be replaced by microservices Y, and also understood that people exist to make that happen. It's not like grandma's knitting, but it could be something like MVP software to get a cofounder and an angel investor.

subtlemuffins 3y ago

https://www.clockworkpi.com/uconsole https://www.clockworkpi.com/uconsole

JKCalhoun 3y ago
Those are cool.

5mv2 3y ago

Have you thought of doing the same with an e-ink screen? I would find it awesome to get work done while in nature.

loxias 3y ago
It's just as awesome as you think. Sadly, those projects always end up getting cancelled.

_Microft 3y ago

Since PCB manufacturing has become super cheap, they could consider having a custom L- or U-shaped custom PCB around the battery box that serves no other purpose than routing signals and power to where they are needed and solder the different boards directly onto that. That would also allow to place supports for this large PCB where they are convenient instead of having to separately mount each of these small PCBs to the case. With less cables in the way, they might get better airflow in the case as well. Edit: I guesstimated the size and think that they could get five pieces of such a board for less than 20€, including delivery.

sgtnoodle 3y ago

I hope they used something other than PLA. I've made some really nice enclosures that warped over time from heat.

bullen 3y ago

What SoC is this using? For the life of me I can't find it in the article? Edit: ok it's a CM4? on the back of the display... For others searching for the secret sauce: BigTreeTech Pad 5