Sending Supercapacitors Through the mail for datalogging. - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: May 10, 2014, 03:46:10 am
content: Hey all, for a long time I have thought that it would be neat to send a device through the mail, most likely an arduino (or more likely attiny84 or 85) with an accelerometer and SD card to log whatever forces it underwent on it's trip, however batteries are usually restricted, and I got thinking about supercaps possibly being a solution. $10 can get you a 10 farad 2.7v super capacitor on ebay, I'm not sure but I have a feeling that would run a hell of a long time on something using as much power as a couple LED's. $30 can get you a 400 farad capacitor (though that's more than I would want to spend probably.Anyways, I'm just curious to hear your thoughts on this, I figure I could just send it to a relative in BC a few provinces over as a trial run but I think it would be neat to set it up securely and mail it off to dave, so that he could grab the data from the SD card, graph it out, and maybe even send it back if it was small enough that it would be cheap.One issue I think is that the SD card needs 3.3v so I'd need to find a higher voltage supercap.

author: TVman
author_rank: Frequent Contributor
timestamp: May 10, 2014, 03:57:37 am
content: TIP: If you don't want to pay 30$ for a capacitor(I think) look in PSU,s.They should have at least 1.

author: XOIIO
author_rank: Super Contributor
timestamp: May 10, 2014, 03:59:32 am
content: Quote from: TVman on May 10, 2014, 03:57:37 amThose ones are usually only 8200uf at most, and that's fairly uncommon. I've never seen a supercap in a PSU.

author: TVman
author_rank: Frequent Contributor
timestamp: May 10, 2014, 04:03:42 am
content: I have seen super caps in A few power supplies before while taking apart stuff.I also had no idea why it was in there................

author: XOIIO
author_rank: Super Contributor
timestamp: May 10, 2014, 04:05:50 am
content: Quote from: TVman on May 10, 2014, 04:03:42 amWhat were the ratings? I'm guessing they were decently new. Even on big UPS power supplies they don't use supercaps.

author: TVman
author_rank: Frequent Contributor
timestamp: May 10, 2014, 04:07:39 am
content: The thing lasted about a week on a LED.

author: XOIIO
author_rank: Super Contributor
timestamp: May 10, 2014, 04:14:50 am
content: Quote from: TVman on May 10, 2014, 04:07:39 amNice, a couple of those together and you have some pretty good life on something that could charge as you dump the data it was logging.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 10, 2014, 04:40:10 am
content: Aren't the battery restrictions only for lithium based batteries above a certain size and batteries that could spill? I don't think there are any restrictions on alkaline or even NiMH.

author: mariush
author_rank: Super Contributor
timestamp: May 10, 2014, 05:26:34 am
content: Lithium batteries are restricted. Other types aren't (but sometimes the post office employees are too lazy or don't care about the rules and prefer to simply mass-refuse any kind of battery)Power supplies don't have supercapacitors (well, most regular ones).Supercapacitors are regularly used in products (Xbox 360 for example) but mostly for battery backup replacement... hold important settings, store time etc... so very low current devices.How much your product will last on supercapacitors will depend on its current consumption and the voltage you want and how you use the energy stored in the supercap.If you just connect the supercapacitor to your product, it's not going to last long, because as soon as the supercapacitor discharges down to 1.8v (the lowest voltage your product runs at), your product will die. From 0v to 1.8v there's still more than 50% of the energy stored in the supercap.You would have to reduce the current consumption of your product, and you'll have to run it at lowest voltage possible and the you would normally use a boost regulator to convert a wide range of input voltage to the voltage your product needs.The boost regulator will make a lot of difference, there are boost regulators that boost voltages as low as 0.6v to higher voltages (likeisl9111for example), other regulators need at least 1.2-2v to work.I've personally used a 25F 2.7v supercapacitor along with LT1308 to boost 1v-2.7v to 6v (because while the meter works with as low as 3v, it shows low battery at around 5.7v) to run a Uni-T UT61E for a bit over an hour... I've made a series of videos about ithere. LT1308 (see its pagehere) works with 1v or more and is more efficient when the input-output difference is smaller.. were it to boost to 2.5v it would have been a different story. At 6v out, it's only about 70-75% efficient.There's also SEPIC regulators, which can take something like 2.7v and convert down to 1.8v or whatever your product uses, and when the supercapacitor voltage goes down below 1.8v, they can switch to a boost mode, raising the voltage to 1.8v.. for exampleLT1613is one of those.

author: miguelvp
author_rank: Super Contributor
timestamp: May 10, 2014, 05:47:32 am
content: Are there any energy harvesting chips that can maintain or extend the supercap?Motion mostly since you can't get much sun inside a package (the best at harversting) RF is too tiny (under 1 uW).If there is no movement go to sleep, on motion datalog and use the harvesting chip to maintain the power, on KHz vibrations (motors) you might get over 500 uW, but watches can maintain with only around 4 uW by your hands movement.Thermal harvesting is good too, but you have to keep a temperature differential so not sure it will work on your application.

author: tom66
author_rank: Super Contributor
timestamp: May 10, 2014, 07:40:57 am
content: Quote from: TVman on May 10, 2014, 04:03:42 amThat's odd, the only reason they would usually do that is so that they can run without input power for some time, so were these uninterruptable PSUs? I've seen a nice one from Rubycon:http://www.rubycon.co.jp/en/catalog/e_pdfs/power/DCH20_e.pdf4 seconds max under full load though is somewhat limiting.

author: SArepairman
author_rank: Frequent Contributor
timestamp: May 10, 2014, 12:30:13 pm
content: the chances that someone will detect your illegal batteries are low. just be sure to package your product in a way so that it does not set an air plane on fire if the arduino shorts out. preferably package it so that even if it goes catastrophic it does not leak any smell.i think their mainly pissed about their stuff catching on fire, a charged supercap could do that too.i could imagine a weird smell in a cargo hold causing all sorts of shenanigans.

author: David Hess
author_rank: Super Contributor
timestamp: May 10, 2014, 01:41:52 pm
content: Just use some alkaline batteries. They are inexpensive for their capacity and safe for shipping. If your sensibilities require rechargeable batteries, then use NiMH cells.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 10, 2014, 08:10:20 pm
content: Quote from: David Hess on May 10, 2014, 01:41:52 pm++ this. a totally pedestrian pair of 2500 mAhr batteries is basically the equivalent of a 3000 farad "super duper ultra cap" with less self discharge and a more stable output voltage. Supercaps have plenty of uses -- primarily their fast charge/discharge rates and the ability to be cycled many times, but this is not a good application for them.

author: scientist
author_rank: Frequent Contributor
timestamp: May 10, 2014, 11:34:50 pm
content: You could just use a coin cell, those definitely aren't restricted as I've gotten them in the mail. Just don't attach anything odd looking to it or you'll get a visit from the coppers.

author: pipe
author_rank: Contributor
timestamp: May 11, 2014, 02:32:19 am
content: It is of my understanding that the restriction for batteries is not batteriesper se, but rather that it is not generally allowed to ship powered-on electronics. There could be various reasons for this, electromagnetic forces messing with the sorting machines, easier to detect bombs, reducing the chance for packages catching fire, etcetera. I may be talking out of my hat here, but it's worth checking with your local regulations before you ship something that will register on their EMF-meters.

author: rs20
author_rank: Super Contributor
timestamp: May 11, 2014, 03:53:20 am
content: FWIW, many tinyAVR microcontrollers have an intergrated boost controller that can boost from 0.7V to 3V, which is actually within spec for (at least some) SD cards (datasheet). That way, you can use a single alkaline cell, which is much safer and more legal than a lithium cell.If Dave doesn't express an interest in receiving the package, I'd be happy to (obviously as a second choice with less pizzazz) -- I'm also based in Sydney.Quote from: scientist on May 10, 2014, 11:34:50 pmJust because something happened once doesn't make it legal. Dave didn't send CR2032 cells out with his uCurrents for this very reason.Quote from: pipe on May 11, 2014, 02:32:19 am"The" restriction? Lithium cells are definitely restricted, whether in a circuit or not (it turns out the bare cells sometimes turns themselves into circuits spontaneously...) But you're right that there may beseparaterestrictions on powered-on electronics.There are two options here. The first is to check the regulations, and if it turns out that what you want to do is not specifically prevented, be completely open and transparent about it. The second option is obvious.

author: XOIIO
author_rank: Super Contributor
timestamp: May 11, 2014, 04:06:19 am
content: Quote from: rs20 on May 11, 2014, 03:53:20 amCertainly some interesting ideas, it will be a while before I get around to doing this, I am going to check regulations and get more info about this. I also have a few ebay voltage step up converters that can take 3.7 volts up to 40 volts, I'm going to use one for a mini lithium-ion battery powered variable power supply, just need to figure out how to be able to get the voltage to 0.First I'd probably get the circuit working (still need to get these accelerometers to work with arduino, I tried quite some time ago and they were acting odd), find out how much power it uses, find a way to get that down as low as I can and find a good solution to power it for a somewhat-long time.Even cooler would be to send a GPS device as well to track it's path at the same time, but that would take a lot more power, and would probably not get through.

author: rs20
author_rank: Super Contributor
timestamp: May 11, 2014, 04:25:57 am
content: Quote from: XOIIO on May 11, 2014, 04:06:19 amIt's hard enough to get a GPS signal in the passenger cabin of a plane let alone the cargo hold. But I suppose you might have some luck in-between flights. I'd probably include a barometer chip instead, not so much concern about power consumption. See if you can find a way of doing the full 6-axis accelerometer/gyroscope thing as well :-)Another thought: more dangerous goods are shipped by sea, for obvious reasons. When you're looking through the regulations, sea if there are more relaxed regulations that allow this. We all know what plane flights are like; capturing the gentle rocking of a container ship instead would be pretty excellent (can you still get mail shipped by sea??)This is just me, but I'd avoid Arduino for the final product because the smaller the final product is, the less threatening it looks. This project can easily be implemented on a custom PCB no larger than the AA cell powering it. Arduino's fine for initial prototyping though, of course.

author: XOIIO
author_rank: Super Contributor
timestamp: May 11, 2014, 04:39:38 am
content: Quote from: rs20 on May 11, 2014, 04:25:57 amWell, I say arduino, but I will just be programming an attiny85 or 84 using the arduino software, though I do have some pro mini's from ebay, but those have LED's which I'd have to remove.

author: Psi
author_rank: Super Contributor
timestamp: May 11, 2014, 05:18:42 am
content: Quote from: scientist on May 10, 2014, 11:34:50 pmWhen i ordered 400x CR2032 from digikey they were delivered on a hazgoods truck and the box was labeled hazardous with a warning about 'lithium batteries within'.So its probably also related to the quantity you order.

author: XOIIO
author_rank: Super Contributor
timestamp: May 11, 2014, 05:52:49 am
content: Quote from: Psi on May 11, 2014, 05:18:42 amHow many watches do you own?lol

author: G7PSK
author_rank: Super Contributor
timestamp: May 11, 2014, 08:40:55 am
content: It's legal to send batteries in the mail as long as they are contained in an electronic devise or a sealed container,what is not allowed is to send them airmail. I had a copy of the new regulations a few months ago most likely still have them filed amongst all the other junk.The post office here in the UK already uses such devices to check on package handling forces.

author: Fsck
author_rank: Super Contributor
timestamp: May 11, 2014, 08:51:07 am
content: Quote from: G7PSK on May 11, 2014, 08:40:55 amrules are different in different countries. but generally, air cross-border shipments clear customs easier without batteries. and for some postal services, illegal for lithium batteries if you get caught: ie hong kong post

author: Psi
author_rank: Super Contributor
timestamp: May 11, 2014, 09:30:23 am
content: Quote from: XOIIO on May 11, 2014, 05:52:49 amThey were for powering electronic ID tags for a gaming event.

author: pipe
author_rank: Contributor
timestamp: May 11, 2014, 11:41:47 pm
content: Quote from: rs20 on May 11, 2014, 04:25:57 amShipping a powered-on barometer on a plane? If they catch you, you'll have a hard time explaining yourself to the CIA or a similar agency.

author: echen1024
author_rank: Super Contributor
timestamp: May 12, 2014, 03:59:17 am
content: I've always wanted to do this. I have thought just a lithium cell would work. It would be fun to use a 6 axis gyroscope+timer and try and create your own inertial navigation system.

author: rs20
author_rank: Super Contributor
timestamp: May 12, 2014, 06:41:59 am
content: Quote from: pipe on May 11, 2014, 11:41:47 pmI see where you're coming from, although a) a barometer that's connected to nothing larger than an AA cell??, and b) is an accelerometer really any worse? I reckon I'd be able to detect when a plane is in flight using accelerometer alone very easily...