# Sunday, 07 March 2010

Got a new toy recently. This here is the Sapido GR1102


It's basically a compact internet router.


So you can use this to share a hotel internet connection and what not, just like a normal router. But of course if it was just another compact router, I wouldn't have gotten it. :P

Along with a couple of other features which you can find out about on the product website, the 1st reason that I got the Sapido is that you can do this.


You can plug in a supported USB 3G modem which can then be shared wirelessly. This is especially handy when you got to meetings in other people's offices and you'd rather not (or are not allowed to) connect to their office network to get internet connectivity. You might argue that you could just connect the modem to your notebook and do the same thing, but what if you had multiple people from your office attending the meeting? Even though you can use internet connection sharing in Windows to share the connection, a dedicate device offers better performance... and your machine doesn't wait cycles trying to act as a router.

All this is fine, WHEN you have a power plug to connect to though. That's why here's the other reason I got this nifty little thing.


The GR1102 is able to be powered by 5V delivered via a USB mini cable. Or if you swap out the AC plug with the supplied connector.


You can then power it with DC current ranging from 5V ~ 12V. It sounds GREAT in theory, all I have to do is bundle this along with any one of my USB power supplies and I can be a mobile hotspot wherever I go. But what you can't see is the current requirements. Let me adjust the image so you can see the writing on the power socket more clearly.


It says "5-12V Min 10W". Now how would you go about getting 10W from 5V? It would mean that the power supply would need to be able to deliver 5V 2Amps(!) Checking with the Sapido website I found out that you don't actually need 2A, but rather just 1.5A. This is still a VERY high current requirement. As I mentioned in my car charger article previously. Sometimes it's not just a matter of volts but also amps in order to power your devices. Let me give you some examples of 5V power sources you have access to. Your computer's USB port is rated for 5V 1A, so the Sapido can NOT be powered by just ONE USB port, so you'll need to use a Y cable to power it. A typical USB battery source like what I have, outputs 5V but in varying current ranges from 500MiliAmps (apologies to people who actually know how to write the proper current notation, cause I CLEARLY DON'T!) to 1A. This is because they typically use some form of a 3.7V LiIon battery in them and then boost the voltage to 5V lowering it's current capability as a result.

So after futilely trying out a few other external batteries in the market, I figured I needed to build my own power source, a battery that clearly delivers the required voltage without passing through any voltage converters. I did the math and decided that I could build a battery pack out of EIGHT AA BATTERIES (8 x 1.2V = 9.6V, y 1.2? Rechargable batteries mar!) But I decided to try this first.


This is what we call a SLAB (Sealed Lead Acid Battery), You don't usually see one on it's own like this but it's used in thing's like UPS's, Motorcycles, and other equipment.  It's a good choice for powering the Sapido because SLABs have (AFAIK) high current capacity, It's NOT a good choice for portability because SLABs are HEAVY! This one weighs errr.... more than 500 grams less than a kilo.

While SLABs are rechargeable batteries, I don't have any experience in building whatever that will recharge the battery so I referred to Adrian's old battery extender guide since he used a SLAB before. So half an hour later and again reminding myself I have no idea how to solder connector plugs properly I ended up with this.


And it works perfectly!! The battery supplies enough power to the router and I have my mobile hotspot. Or do I? I realized that not many people have actually seen a SLAB before, in fact I'd think that most people would have seen SLABs being used as bomb triggers in movies or TV shows. So I told myself carrying a SLAB with wires and tape all over it might not be such a good idea right now. I head on over to my favorite place for finding weird shit nowadays – Daiso. And I ended up with this.


For those of you who are thinking WTF? This is an INSECT CAGE, I decided to get this one instead of other normal cases because the router can get QUITE hot when in use, so the open ventilation should be sufficient to cold it off. I used the straps from my previous attempt at a car pc to secure the devices.


The 2 things just barely fit into the case itself, I haven't really done a proper test run yet cause I haven't been able to obtain a proper adapter to charge the SLAB and thus I don't know how long the power will last (Unless someone tells me that it's ok to pump 9V into the SLAB to charge it even though it says it's charging voltage is 7.2V) I'm really interested in seeing if the router will melt the cage after prolonged use!

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