"Best" way to power the oak off the grid?

[dlichterman]

I'm working on putting together a weather station with my Oak and I want to power it off solar.  Does anyone know the part number or actual spec on the LDO that is used for the VIN pin - it says 4.5-12V but does that mean no higher (like 12.8 for a lead acid battery)? I guess that's a linear regulator though....so maybe I would be better off with the lipo shield and a 5V USB input from a solar panel with a switching regulator?

Any tips would be appreciated.

[defragster]

The LDO used was specified in an UPDATE on KS - and I reposted that link or details on the forum some weeks back.  If you find that you might get your answer.

First guess (or memory) - even if it can handle that voltage or above is that might be too much voltage (i.e. heat) to drop for the current and thus the 12V spec - so pick up a switching regulator or something to safely get it down to 5V first. I think that is why Erik offered one in the KS - and it may be in the store.

[dlichterman]

Yeah I kinda figured that the 12V to 5V drop was a huge waste so it'd be best to try not to use them. I picked up a solar panel from amazon last night and will be using that to power the oak from the USB port.

Anyone know if the lipo shields are being shipping right away if I order one now? Seems like the lipo shield plus good 5V in seems like the solution. I played around with the ESP.deepsleep function and boy that drops the power consumption quite low.

[defragster]

Searched LDO and found my prior post: http://digistump.com/board/index.php/topic,1926.msg8649.html#msg8649

It can go up to 16V - but can get hot enough to shut down near 7V.  Due to small size and the heat involved.

[dlichterman]

Yeah, that's a ton of heat to dissipate and lots of lost power.  I picked up a 5V solar panel, a 5V boost converter, and I have a lipo charger coming tomorrow from amazon to use with a recycled lipo from a laptop battery....so in theory this kludge should work and be relatively efficient.

[dlichterman]

defragster - I finally got around the reading the datasheet on the LDO:

Input Voltage Range VIN ................................ 2.5V to 16V

So...... I guess I could directly connect the lipo cell to the oak without a 5V boost?  I would connect this via the VIN pin?

The oak pinout sheet says minimum 4.5 on VIN though.....but the kickstarter message says "This is one of the very few linear regulators that can - produce 3.3v at 500ma or more, do so even with a single LiPo cell input, and also handle inputs over 5.5v, while producing very clean power."......so.....I guess I can hook up the battery to VIN?

I guess that is implied later down with the JST header spot next to the USB?

[PeterF]

Yes, you should be able to just connect the lipo to the Oak via the VIN connection or the JST header / connection point. Depending on your power usage, I'd make sure the lipo has a protection circuit, or use a board like this one between the battery and the Oak, so the Oak can never run the battery completely flat and kill it.

[dlichterman]

That is exactly what I already have - and then I'm boosting to 5V only to have it drop back to 3.3....so I will try hooking it up direct next! Thanks!

[dlichterman]

To follow up - I soldering on a JST-PH header and hooked up direct to the output of the TP4056 module and it's working great!

[PeterF]

Great to hear. I'll be doing the same with a TP4056 and a solar charge module, so should be interesting to see how much life I can elk out of the battery. Just following up on the power usage stats of the oak as my much better power meter arrived in today's post, so I thought I'd post some stats of what my Oaks are like. Power consumption in DEEP_SLEEP is minuscule - most of it is probably the power LED!

Oak #3 (a DS18B20 sensor node) (5.3v supply)
DEEP_SLEEP = 0.0009A (so less than 1mA)!!! Picture of meter
Running = mostly 70mA, ranges from 30ma to 100mA, workload is starting up, connecting to wifi, publishing to particle

Oak #1 (a viewer unit with 2.2" TFT LCD) (5.3v supply)
Running = averages 96mA, workload is waiting for particle publish events. also powers LCD (backlight always on). Picture of meter

Oak #2 (another DS18B20 sensor node) (4.98v supply)
DEEP_SLEEP = 0.0009A
Running = mostly 69mA, ranges from 29mA to 70mA, workload is starting up, connecting to wifi, publishing to ubidots and thinkspeak

Will post a youtube clip or two showing the oaks power usage over time in the morning...

[dlichterman]

I have on of those crappy USB meters with 2 digit resolution - it was showing 0ma in deep sleep(lowest actual reading can be 0.01A) and 70ma(0.07A) when waking up and shooting the data to wunderground.  Has been working great with the TP4056 connected to a small solar panel.  Might even change the update frequency to every 5 minutes instead of 10 minutes. I should work out the math on actual consumption - but it's still insanely tiny in deep sleep.

[PeterF]

That sounds like the meters I had before (and still have around) - one was a 7 segment led display one which flipped between volltage and current, and the other is a nicer oled display that has volts, amps, watts and cumulative usage... but they were both limited in resolution to 2 digits. I really need to get on with attaching my oak to a TP4056 + lipo + solar!

[PeterF]

Ok, I know this thread is a little quiet atm, but I just wanted to say how shocked I am over how stable and power-friendly you can make the ESP8266/Oak... I have my unit that posts to thinkspeak and ubidots every 10 minutes now running directly from a 1000mah lithum cell, and a solar charge module + solar panel, and the voltage hardly sags overnight, and charger indiates done pretty early on in the morning, so I could probably half the battery size and still run without any issues!!! Far cry from my NodeMCU 1.0 development board!

[exeng]

pfeerick,

I'm looking to remote a pool temp probe with the Oak and power it via Solar / Lipo cell combo. So I'm very interested in what you are using for a Solar panel and it's spec's. I would prefer to have something small as I want it to be portable. Same concept... sleep and wakeup at regular intervals to post temperature to Particle, Thinkspeak, and a Blynk app.

Also, is there a preferred source for the TP4056?

[PeterF]

For me, no preferred source for the TP4056s... just whatever turns up on eBay at a good price - they're a good price to start with so there aren't likely to be any fakes. I use this version of them as they also have a protection IC to prevent the battery from being over discharged, so don't have to worry about protected or unprotected lithum cells.

For solar charging, I have a load of these solar charge breakouts/ICs, and they seem to work well. I use these solar cells in conjunction with that - doesn't charge the hardest if you believe that solar chip can do 500mA, but it was the best glass solar panel I could find... the epoxy ones keep crazing on me due to the harsh sun we have here.

Hope that gives you some ideas