# Saturday, 13 March 2010

Today I went to pick up some parts to complete my Mobile Hotspot Project, first of all I decided to get a smaller sized battery since the one I had original, is big and bulky. So I wanted to get something that's smaller and easier to carry around.

DSC06275

So I got this, 6V 1.2AH battery. My first surprise was that while the battery capacity was about 1/4 of the big battery, it costs TWICE as much! While I was soldering the connection wire I learnt something new. I should solder the connector first, before soldering the wires to the battery. Because I soldered the wires to the battery first while I was soldering the connector... I shorted the connection with my soldering iron, sparks flew! Good lesson...

So after the smaller battery was completed and tested to be working I created the other component which I wanted to make.

DSC06276

A 4AA battery holder, with normal alkaline batteries these would theoretically give out 6V of power which should be more than enough to power the router. I measured the current with a multimeter and got a nice reading of 6.6V, So I went ahead and plugged it to the router. And I was happily surfing the net with AA batteries.... for about 10 minutes. Then the router started flickering on and off, a good indication of low power scenario. I unplugged the batteries and measured the power output and I got... 5.5V!?!?!?

I figured it's because that when an alkaline battery is used out the voltage gradually decreases on a slope. Unlike a rechargeable battery which is at the same voltage for most of it's usable lifespan and then drops. I guess the way is to introduce more power into the loop.

Luckily I was prepared for this scenario. While I was thinking of using AA batteries to power the setup, I was planning to use rechargeable batteries. But.. a rechargeable AA battery only has a voltage capacity of 1.25V, 4x1.25V = 5V. Cutting it a bit close so I thought of an idea, which is to make a power booster to bump up the voltage.

DSC06277

This battery case will be linked in series to the power source it's connected to, boosting the voltage of whatever it's connected to by 3V. Once I plugged this in I can again power the router... for a while, once again I could see a very drastic drop of power in the alkalines once hooked up to the router. It's obvious that alkalines aren't the best source of power to be used in this scenario.

I then decided to work on a power switch so I can turn power on and off when I wanted to without having to disconnect the power source to the component.

DSC06278

You might have noticed that each piece is more or less interchangable. This allows me to have some form of extendable system, for example I can have the router powered by 4AA batteries, as well as controlled by the power switch.

DSC06280

Then if needed to, I can plug in the booster pack.

DSC06282

Depending on the situation, I can plug in an extension wire, and then the lightweight 6V battery.

DSC06283

The reason I needed this extensibility was because I had a crazy idea, and it involves this thing.

DSC06284

A belt strap... cause I want to try and do this.

DSC06285

Hook everything up to it and really carry it around in a portable manner, the problem of course is that if people saw a SLAB strapped to someone, they probably would think that I'm a suicide bomber or something!

Anyone have a good idea to make a belt like this look less like a suicide belt?


Saturday, 13 March 2010 21:51:42 (Malay Peninsula Standard Time, UTC+08:00)  #    Comments [0]  | 
# Friday, 12 March 2010

There are times when I wish I had more training and understanding about how to build electronic hacks. Especially at times when it involves AC current.

DSC06270

Here I've taken an AC/DC adapter, replaced it's head with a composite jack.

DSC06271

Just so I can charge the SLAB I gotten for my portable hotspot project.

DSC06273

And I don't think I chose a safe spot to do it too!

DSC06272

Well, power should flow from the higher 7.5V of the adapter to recharge the lower 6V of the battery.. I THINK! The charging method matches what Adrian used in his battery extender project. But heck, I'm not sure if I done everything right!

Also, the power adapter is FICKLE!! Sometimes when I turn it on it pumps out 3.5V, sometimes.. it pumps out 7.5V.. it's weird! And... how do I know if the battery is being charged? Well... the adapter was hot for a while. And I think at charge the battery has a 6.5V rating.

Maybe I should abandon project Mobile Belt?

image


Friday, 12 March 2010 22:26:41 (Malay Peninsula Standard Time, UTC+08:00)  #    Comments [0]  | 

DSC06269

Just one more!


Friday, 12 March 2010 09:50:27 (Malay Peninsula Standard Time, UTC+08:00)  #    Comments [0]  | 
# Sunday, 07 March 2010

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

DSC06254

It's basically a compact internet router.

DSC06255

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.

DSC06257

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.

DSC06258

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.

DSC06260

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.

DSC06261

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.

DSC06263

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.

DSC06266

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.

DSC06248

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.

DSC06249

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!


Sunday, 07 March 2010 21:27:32 (Malay Peninsula Standard Time, UTC+08:00)  #    Comments [0]  | 

I still remember taking this picture.

DSC01929

This was in 2008, WZ was just slightly over a year old then but he wanted to try and drive. And now...

Soon... soon...


Sunday, 07 March 2010 00:26:10 (Malay Peninsula Standard Time, UTC+08:00)  #    Comments [2]  |