Forum Rule: Always post complete source code & details to reproduce any issue!
Page 2 of 4 FirstFirst 1 2 3 4 LastLast
Results 26 to 50 of 76

Thread: Appallingly small LiPo charger add-on for Teensy 3.1

  1. #26
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    The three smaller pads in the center are the active ones. The switch connects the center pad with either the left neighbor or the right neighbor. The larger pads are just for anchoring the switch to the pc board and are not signalized.

  2. #27
    Great, that's what I thought. But if this is just an on/off switch, only one neighbor would be active, right? And the other would go to nothing and leave the circuit open. Or is it more complicated that?

  3. #28
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    Center small pad goes to VIN. One side enables the Teensy by connecting battery and VIN, the other is to ground.

  4. #29
    Thanks for the quick response.

    1) Would it work to solder a lead to the VIN connection between the add-on and the Teensy instead of to the middle pad of the switch (and perhaps to the ground pin instead to the ground pad of the switch)?

    2) Is it possible to use a single-throw (on/off) switch here by connecting the battery and VIN and not connecting VIN and ground? Or would VIN and ground need to be connected when the switch is turned off.

  5. #30
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    Yes to both, and this might be the easiest way to do this.

  6. #31
    Great, that's very easy. Could you tell me which pad, B or D, is the connection to the battery? I'll just put a single-throw switch between that and the VIN pin.
    I appreciate the help.

    Click image for larger version. 

Name:	teensyaddon.jpg 
Views:	114 
Size:	68.1 KB 
ID:	3951

  7. #32
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    D is +Vbat, B is GND, C is Vin.

  8. #33
    Member mixania's Avatar
    Join Date
    Oct 2014
    Location
    New York, NY
    Posts
    20
    One quick question, sorry if it was somehow mentioned before in the thread.

    Lets say if my project consists out of a LiPo battery, a 3-6V solar panel and this add-on board on a Teensy 3.1. The project therfore relies completely on solar energy and energy stored in the Li-Po. Will I be able to safely attach the solar panel to Teensy's Vin while the the add-on board safely charges the Li-Po? Is there some possible risk when wiring it this way? Or is the board designed to effectively deal with inconsistent power coming from solar panels as well as the easy 5V coming from USB connection?

    Thank you in advance! I'm also thinking of ordering the M41T62 Real Time Clock Add-On and maybe the SPI Flash Memory . Certainly the best products for Teensies out there I've seen sonfar.
    Last edited by mixania; 03-26-2015 at 05:58 PM.

  9. #34
    Member mixania's Avatar
    Join Date
    Oct 2014
    Location
    New York, NY
    Posts
    20
    Also, will the Teensy still be provided with power while the LiPo is charging? Or does the current switch off until the LiPo is fully charged?

  10. #35
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    I am in the process of doing something quite like this for my remote logging project, but haven't got a working test setup yet since I'm still stuck on getting the RTC interrupt to work as I want. Anyway, I would connect the solar cell to the DC IN port of the LiPo charger. As long as it supplies > 4 V it will charge the battery, whether you have the switch set to allow the Teensy access to Vin or not. When the battery is fully charged, the DC power in is ignored. In any case, it never gets to the Teensy. Only the battery can power the Teensy. And the power is supplied to the Teensy while the battery is charging. But I would recommend you just try it and see if it works the way you want.

  11. #36
    Member mixania's Avatar
    Join Date
    Oct 2014
    Location
    New York, NY
    Posts
    20
    So if the Teensy is only able to draw current from the LiPo and not from the solar cell, would that mean that the chrager would be constantly charging the battery even if there is constant current coming from the solar cell? In other words, the Li-Po will never get discharged during a sunny day since the charger will constantly sense that the battery is slightly discharged and therefore constantly charge it. If this is correct, won't it produce too much stress for the battery?

    Regardless, I'm going to go ahead and order the board just for the support

  12. #37
    Member mixania's Avatar
    Join Date
    Oct 2014
    Location
    New York, NY
    Posts
    20
    Ahh, out of stock. Got waitlisted.

  13. #38
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    The MAX1555 detects the state of charge and there is some hysteresis in the charge cycle so it won't continuously try to charge the battery, but the battery won't get fully discharged until the sun sets!

    I usually make these LiPo battery chargers in batches of 10 or 15 but right before I left for my week-long trip someone ordered nine of them and cleaned out the supply. I'll make more when I get back to Pesky Products World Headquarters this weekend.

  14. #39
    Member mixania's Avatar
    Join Date
    Oct 2014
    Location
    New York, NY
    Posts
    20
    Thank you @onehorse, that answers my question! Am looking forward towards your next batch.

    Michael

  15. #40
    Senior Member
    Join Date
    Nov 2012
    Posts
    412
    @onehorse

    Your Teensy charger is great!

    Since the new Teensy-LC Mo+ ARM stamp sleeps in uamps have you ever entertain the thought to also providing a battery monitor aka fuel guage in addition to your lipo charger?

    Link design ref: https://www.kickstarter.com/projects...nd/description
    Last edited by t3andy; 03-27-2015 at 01:26 AM. Reason: correction

  16. #41
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    This battery monitor talks to the host (Teensy in this case) via I2C although battery status is available via an interrupt also. In both cases, host intervention is "required" unlike the basically passive existing
    charger.

    But more importantly, the part is ~$2 which means I would have to charge $15 for a charger with the monitor as opposed to $10 for the current one. Is it worth 50% more for a gas gauge? I have been thinking of redesigning the LiPo battery charger and I have a target chip in mind that does allow a battery fuel gauge capability, also with multiple alerts. The alerts would likely be different colored leds, maybe from a small rgb led, and maybe a host interrupt but this isn't really necessary. The decision is who is responsible for checking an alarm, the user or the host?

    Also, I'd like to keep the cost low.

  17. #42
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Posts
    9,021
    Here is a potential software hack: https://forum.pjrc.com/threads/26117...-battery-alert

    Old thread covers LiPo power drop and reading the chip 3.3 voltage level - came alive as someone wondered if the LC could do it too.

  18. #43
    Has anyone had any trouble using this with the LC? I haven't tried it yet, but it should work just fine, right?

  19. #44
    Senior Member+ MichaelMeissner's Avatar
    Join Date
    Nov 2012
    Location
    Ayer Massachussetts
    Posts
    3,063
    If you are redesigning the lipo charger, I just got hit with the fragility of the on/off switch. As I've mentioned, I tend to prefer stuff on top of the Teensy, instead of underneath it.

  20. #45
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    Posts
    9,021
    MM - will you be able to work it back to life?

    Was that more from repeated use, or just applying non-linear force? I have 3 of these on hand unused so far.

  21. #46
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    Hi Michael,

    Yes, there is a similar ALPS switch with mounting lugs which would tend to make the switch a bit more robust. I will try to use this to reduce switch failures. It costs a little more, as does the slight increase in complexity of the new design so that I will have to ask more like $15 instead of the $10 I am asking for the current LiPo battery charger.

    I don't like top mount for this component since the USB plug is in the way. Of course, it can always be mounted on top but upside down!

    If you have had a mishap with your LiPo battery charger send me PM and I will arrange a replacement gratis. You likely got one of the first few that didn't benefit from the extra solder I currently apply to keep the dang switch in place. Extra through-hole lugs will help a lot.
    Last edited by onehorse; 04-08-2015 at 09:27 PM.

  22. #47
    Senior Member
    Join Date
    Nov 2012
    Posts
    412
    But more importantly, the part is ~$2 which means I would have to charge $15 for a charger with the monitor as opposed to $10 for the current one. Is it worth 50% more for a gas gauge?
    Yes, there is a similar ALPS switch with mounting lugs which would tend to make the switch a bit more robust. I will try to use this to reduce switch failures. It costs a little more, as does the slight increase in complexity of the new design so that I will have to ask more like $15 instead of the $10 I am asking for the current LiPo battery charger.
    How about a 3 pin switch jumper and a battery fuel/gas gauge? The fuel gauge is worth more!

  23. #48
    Senior Member+ MichaelMeissner's Avatar
    Join Date
    Nov 2012
    Location
    Ayer Massachussetts
    Posts
    3,063
    Quote Originally Posted by defragster View Post
    MM - will you be able to work it back to life?

    Was that more from repeated use, or just applying non-linear force? I have 3 of these on hand unused so far.
    I believe it was non-linear force. I was trying out various positions of mounting before soldering it to the Teensy, and I was trying to flick the switch to see if I could enable it in the position I had it in. A better solderer than I might be able to reattach the switch. So, I was just going to order another one. As onehorse says, I was one of the first people to order it, so it might not have had the extra solder he now applies. With the discussion about it, it had peaked my interest, and I was about to setup my soldering station (which for various reasons had been packed away for the winter).

  24. #49
    Senior Member onehorse's Avatar
    Join Date
    Apr 2014
    Location
    Danville, California
    Posts
    921
    I finally made a decision on the next generation of LiPo battery charger chip, it is this one from ST Microelectronics:

    http://www.mouser.com/Search/Product...ey511-L6924UTR

    How about a 3 pin switch jumper and a battery fuel/gas gauge? The fuel gauge is worth more!
    The nice thing about it from my perspective is that it is essentially a plug-in replacement for the MAX1555 and significantly smaller. With the substitution of 0402 passives I should be able to maintain the current board form factor and add some flexibility for the user as well as some additional diagnostics including a simple battery fuel gauge.

    The nice think about it from others' perspective is that it allows 100 or 500 mA charge rates from USB and up to 1 A from an AC powered wall wart (i am assuming this means DC in, just like on the MAX1555).

    This new charger should become available for sale at Tindie in the next few weeks.

    It won't meet everyones needs but it will still be appallingly small and fit on a Teensy 3.X.

  25. #50
    Senior Member
    Join Date
    Feb 2013
    Posts
    181
    Before I assume anything...this will also work with the LC teensy? Was going to use it for a project and wanted to dbl check. Also, not sure if anyone else has had this issue, but the battery connector for me was really hard to get into the holes. I had to strip the pins a bit to finally get it to fit and even then it was still really tight and not great.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •