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Battery Power Options

Home Forums Mayfly Data Logger Battery Power Options

This topic contains 16 replies, has 6 voices, and was last updated by  Brett Melbourne 3 months, 1 week ago.

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  • #1806

    Marion
    Participant

    Can the Mayfly be powered by a 4.5 volt alkaline battery pack? For a monitoring station under a bridge or in deep shade this would be an low cost option to supply power for long term logging where solar recharging is not feasible. The borad schematic shows a voltage regulator (SPX 3819) connected to the LiPo battery connectors which appears to be capable of handling the 4.5 volt input.

  • #1812

    Shannon Hicks
    Keymaster

    Yes, you could attach a 4.5v alkaline battery pack to the LIPO battery connection, but since you never know who might come along later and plug a solar panel into the SOLAR jack, it’s good practice to only connect LIPO batteries to that jack. That’s why I designed a separate 2-pin header (unpopulated) on the Mayfly that’s labeled “Ext 5V” so you can solder a little 2-pin header (preferably polarized) on there and connect an external battery pack that way. I like this particular connector/header combo: http://www.allelectronics.com/item/con-242/2-pin-connector-w/header-.10/1.html

  • #1854

    Bert Rubash
    Participant

    I have a related question. Why should I not plug two LIPO batteries to the battery jacks. Is it because I would risk too much charging current? If I refrain from charging, wouldn’t having two batteries plugged in simply extend operating time?

  • #1856

    Shannon Hicks
    Keymaster

    The charging circuitry on the Mayfly isn’t capable of charging 2 parallel battery packs simultaneously, so it’s not advised to connect two packs to the Mayfly if you ever connect a mucroUSB cable or solar panel to it because either of those will start the charging process.

    The second LIPO connector on the Mayfly is for providing a direct connection to the battery for high-current accessories like a GPRSbee module. It’s not supposed to be used to provide a secondary battery input for the Mayfly.

    However, if you take precautions to make sure you never connect a microUSB or solar panel, then theoretically it’s possible to connect two parallel batteries to power the Mayfly, but you run into the usual issues related to parallel battery operation, like making sure both batteries have identical capacity and are charged to the same initial voltage, along with other precautions. Given the dangers of short-circuiting LIPO batteries and causing a fire, EnviroDIY does not recommend that users connect more than one battery to their Mayfly at a time.

    Also, if you connected 2 LIPO batteries at once, you can’t use the onboard LIPO charging circuitry on the Mayfly, so there’s no benefit to using LIPO batteries and you might as well just use a single high-capacity battery pack of a different chemistry (like lead acid or alkaline) if you’re looking for longer lifespan.

  • #1857

    Bert Rubash
    Participant

    Thanks, I’ll avoid plugging in two LIPO batteries.

  • #12843

    Cal
    Participant

    I’m planning to replace some existing datalogging equipment with the Mayfly and keep some of the existing power equipment.

    Today I have several stations each with Campbell Scientific dataloggers & sensors, standalone modems, solar panels, lead-acid batteries and charging circuits. The equipment is all 12v based. My desire is to pull out the dataloggers and modems and replace them with Mayflies + Digi modem modules. I have all the software working which includes interfacing the CS pressure transducers and cellular communications.

    The question is: can I use/keep the existing power (12v 8aH battery, 24v solar panel and charging circuit) and how should I connect to the Mayfly? Also – do I need a LiPo battery to supply the modem?

    Thanks for any ideas/help. – Cal

  • #12845

    Sara Damiano
    Moderator

    Depending on the version of the Mayfly you have, there’s a 12V power input that you can step down and use. If I remember correctly, though, @aufdenkampe once told me he’d had smoother power and less loss using a separate 12V to USB step down and powering the Mayfly via the USB port.

    Unfortunately, though, with either option you would still need a LiPo to supply the modem. The Digi cellular modems require more amperage than the Mayfly can provide on its own so the only option is to power them directly off the battery by way of SJ13. If you don’t have a battery plugged into one of the Mayfly’s battery jacks, the modem wouldn’t be powered at all.

  • #12848

    Cal
    Participant

    Thanks Sara. I think a cheap 12v to 5v phone charger will work well for me then.
    As for the LiPo battery – I will use a small one. Our transmissions are short and the LiPo will be recharged from the lead-acid battery.

    I have the V0.5b version of the Mayfly – so I could use the 12v input. But I’m a little worried though that the voltage may spike above 14v during sunny days. Do you think that would be a problem?

    I have a small disagreement with your last comment: “the modem wouldn’t be powered at all”. I often run my Mayfly + Digi modem WITHOUT a battery! It works (most of the time) so it does get power from my USB source – but I know it’s on the edge. I have the SJ13 soldered.

    Cal

    • #12850

      Shannon Hicks
      Keymaster

      The Mayfly can handle up to 16v input without risk of blowing anything up. I designed it that way so people can power it with a 12v battery that’s also attached to a charger, so their battery sees up to 15v sometimes, but still won’t hurt the Mayfly.

  • #12849

    Sara Damiano
    Moderator

    Oops, yes, sorry, the modem would have power without the battery, just not enough. The naked u-blox SARA R410 cellular chip uses just barely under half an amp at peak. (Assuming you’re using the LTE model.) Add the Digi processor and it’s too much. I’ve never had any luck getting it to connect without a battery. It browns out and stops responding. Often it needs to be completely powered off (or yanked from the board) before it will be happy again.

    I think @acgold might have gotten the Sodaq SARA R410 uBee working with the Mayfly without the solder jumper: https://github.com/EnviroDIY/ModularSensors/issues/228

  • #12853

    Sara Damiano
    Moderator

    Hopefully @aufdenkampe will confirm but I think he went the USB route mainly to avoid power losses in the step down. If you go that way you probably need a relatively expensive 12V to USB to make sure you are getting less loss than the built in step down.

  • #12899

    Cal
    Participant

    Next week I’m deploying several units – Mayfly with XBee using Hologram SIM, logging data from CS451 SDI-12 pressure transducers. They are replacing old 12v systems with Microhard 3G modems and CR300 Dataloggers. The old modems are power hungry and unreliable. The AT&T service is expensive and 3G will go away eventually. The dataloggers have trouble switching power to the modems and their solar charging circuit is unreliable. So I’m getting more reliability at a FAR lower equipment cost and monthly charge while using the existing sensors, enclosures & power (solar/12v batteries). I’m also getting more flexibility since I own the Mayfly sketch and the Internet server code.

    I’d like to confirm a few things I think I know before connecting the power of Mayfly v0.5b:
    1. the Ext 12v input will NOT charge a connected Lipo battery.
    2. the voltage on the solar JST must be <= 6v, not the 20v-1a that’s listed on the LIPO CHARGER section of the hardware diagram
    3. best option is to use a 12-5v USB charger (that Shannon has suggested in other posts) to power the Mayfly and charge the Lipo.

    Thanks, Cal

    • #12902

      Shannon Hicks
      Keymaster

      To address your points:
      1. Any power source connected to the 2 pins labeled “Ext 12v” will power the Mayfly but will not charge any LiPo batteries connected to the two LiPo jacks.
      2. The solar panel connected to the JST jack labeled “SOLAR” should never exceed 6 volts. The charging circuity on the Mayfly uses a small chip that has a 6v maximum input (and 500ma max charge rate). This is the reason that connecting a 12v source to the external power pins (see point 1 above) won’t charge the battery. The 20v-1A note on the schematic denotes the rating of the protection diode, not the input voltage source
      3. Using a 12v-to-5v USB converter connected to the Mayfly’s USB jack will power the board, and charge any LiPo that’s connected to it, so that’s the preferred method for now. Hopefully the next version of the Mayfly will be more flexible about input voltages and charging.

      A couple other points to make:
      If you’ve jumpered over SJ13 to power the bee socket’s Vcc pin (pin 1), remember that the bee socket’s pin will be continuously powered by whatever battery is on the LiPo jack, and will not turn off even if you turn off the Mayfly’s main power switch. If you have a board like the new Digi 4GLTE board, the 4GLTE board will wake up when the Mayfly is turned off since the Mayfly can’t assert the sleep pin anymore. I’ve modified a few Mayfly boards to get around this issue, but it’s not easy, and have now made a tiny new adapter board that goes between the 4GLTE bee and the Mayfly that will solve this problem, along with giving the user some handy status LEDs since the 4GLTE bees have no indicator lights on them at all. I’m hoping to have those adapters in about a month.

      Second, the CS451 needs 6-18v excitation, which the Mayfly can’t provide. How are you powering the sensors, and are you using the SDI-12 or RS232 protocol on them, and how are you interfacing them with the Mayfly? Without an adapter or voltage level shifting circuitry, the higher voltage signal will damage the input of the Mayfly. I’ve made a variety of custom level shifters and voltage boost boards for different sensors (6v, 9v, 12v, etc) or used relays to control power to higher loads. Either way, the signal needs to be conditioned properly before feeding it back to the Mayfly.

  • #12903

    Brett Melbourne
    Participant

    I have a really similar issue (12V powered sensor + SPI-12) that I would appreciate some advice on. We want to monitor solar radiation (shortwave) under forest canopy, for which common silicon diode pyranometers (e.g. Apogee SP212) are not suitable – a thermopile pyranometer is needed. We have two options for thermopile pyranometers. 1) Apogee SP510. Self powered, output range 0-144mV. 2) Campbell Sci CS320. 6-24V excitation, SPI-12 output. We will not be using the optional 12V heater on either of these. Both sensors are actually manufactured by Apogee. I saw in another comment that the millivolt SP510 signal will be noisy with the Mayfly (an amplified version of SP510 is not available). We are working in a low light environment, so noise will be an issue. Thus, I was leaning toward the CS320 due to the SPI-12 output (hence zero logger/cable noise). But the CS320 has the same power issue as the CS451 pressure sensor mentioned above. Which would you suggest for the mayfly? Is it better to tackle the noise/signal amplification issue or the power issue?

    Also, just want to say thanks for all the awesome work going on here – super exciting initiative for ecological monitoring!

    • #12934

      Brett Melbourne
      Participant

      Update. We decided to try the SP510. Seems to work fine with the ADS1115 set to max gain (GAIN_SIXTEEN) with differential measurement. Resolution is 7.8 uV, or 0.14 W m^-2. I ran it for a few days logging every 2 seconds and it doesn’t look especially noisy. We will be trying this out more thoroughly in the coming month.

  • #12904

    Cal
    Participant

    Thanks, Shannon, for your response, clarifications and tremendous work with the Mayfly. Addressing your questions:

    I’m powering the CS451 with the same 12v battery that powers the Mayfly from the 12-5v USB converter. The ground (-) of the Mayfly & battery are common. I could not find anywhere in the Campbell Sci specs the voltage level for the signal. But I did find in the SDI-12 Serial-Digital Interface Standard (SDI-12 Support Group, Utah) that the standard for the signal is essentially 0-5v. So, I plugged the signal line in Digital Pin #7 and it’s been working fine. If I had an oscilloscope I could confirm the voltages.

    Cal

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