I recently posted a review of video cameras, and today's review is about a little helper that makes setting up IP cameras easier.
The helper is a slightly modified compact TP-link TL-WR702N router.
If you're interested in making something useful with your own hands, read on. I hope you'll find it interesting.
I actually got this router back in the spring and used it for quite a while before replacing it with another one. It sat around unused, and I kept wondering how I could put it to good use—until a comment on one of my reviews gave me the idea to modify it.
I'll tell you about the modification later. First, the obligatory part: the packaging, a brief description, and photos of what's inside.
The router arrived in a very neat, sturdy little box. At least, it made the trip in an envelope without any problems.
The end of the box has a very brief list of specs, along with plenty of Chinese characters.
TP-link TL-WR702N, or my new little helperEverything inside was just as neatly packed, with no complaints at all.
The company is a well-established brand, so this level of care is no surprise.
TP-link TL-WR702N, or my new little helperThe complete package includes:
1. Router (though technically, in Russian, it's a “marshrutizator”)
2. Power supply
3. USB-to-microUSB cable
4. A pile of paperwork.
TP-link TL-WR702N, or my new little helperA few words about what's included.
The manual is almost useless, since it's written almost entirely in Chinese.
The USB cable is very good quality—I'd even say it's good, and at the very least it's neatly made.
No complaints about the power supply either: it doesn't get hot in use, looks decent, and does its job.
TP-link TL-WR702N, or my new little helperThe router. The first thing that strikes you when you see it is how bright it is.
The color is a lemon-lime green, and the body itself is white.
There's a sticker on the bottom with the MAC address and serial number. I don't remember for sure now, but IIRC, the serial number is the router's password. Though even the Chinese manual gives you enough clues to figure out how to access the router :)
TP-link TL-WR702N, or my new little helperAfter receiving it and connecting it to my computer, I found a couple of reviews that said this router was the Chinese version—in other words, it was almost entirely in Chinese.
And sure enough, that's what I saw after connecting it.
TP-link TL-WR702N, or my new little helper
TP-link TL-WR702N, or my new little helperFor the most part, the router's menus are exactly the same as those on its English-language counterpart, just in Chinese. Anyone who's set up a router a few times should have no trouble configuring the Chinese version either, especially since you usually only have to do it once or twice.
TP-link TL-WR702N, or my new little helperThe router can operate in five standard modes. For my application, I used Repeater mode.
Access Point
Router
Repeater
Bridge
Client
TP-link TL-WR702N or my new little helperOf course, I tried updating the firmware to get at least an English interface, which would have been more than good enough for me.
But my attempts were in vain.
TP-link TL-WR702N or my new little helperAfter browsing the forums for a while, I found out that you need to set up a virtual FTP server and update the firmware from there.
But it came to nothing: the router just returned an error, and that was the end of it.
TP-link TL-WR702N or my new little helperLater, I read in one of the reviews I linked to above that:
A blue top means English firmware only; the menu interface inside is green.
A lime-green top means Chinese firmware only; the menu interface inside is blue. What a shame—I really liked the color of its case :(
And, of course, I had to take it apart (well, almost).
The router isn't very easy to open: the clips are sturdy, and the cover feels almost like one solid piece with the rest of the case.
After a bit of a struggle, I finally got it open, though the case took some damage too—the plastic is soft, and it left marks.
The soft plastic is actually a good thing, since it's less brittle. That's especially useful for my application.
Inside was a small circuit board and plenty of empty space, which was another reason I decided to modify it.
TP-link TL-WR702N or my new little helperThe router uses an
AR9331-AL3A processor made by Atheros.
DDR SDRAM,
M13S128168A, with a capacity of 16 MB (if I understood the specs correctly).
TP-link TL-WR702N or my new little helperThere are noticeably fewer components on the back of the board, mostly resistors and capacitors, along with a printed Wi-Fi antenna.
TP-link TL-WR702N or my new little helperThe flash memory for storing the firmware is a 25Q160VS1G made by Winbond, with a capacity of 2 MB.
While I was at it, I also took an interest in the DC-DC converter. The router's nominal supply voltage is 3.3 V, so the board has a small 5-to-3.3 V converter.
TP-link TL-WR702N or my new little helperI don't see much point in describing how it works—it's just a router.
I used it for about 4 months as a bridge, or an “extender.” During that time, I never once had to reboot it; it worked great.
But it was in a rather inconvenient spot, and extender mode itself cuts the speed, so it wasn't particularly fast.
Its Wi-Fi power/range isn't great, which is down to the small antenna, but I wouldn't call it terrible either—it works fine.
There's not much else to say about the router, so I'll move on to the modification I planned last summer but only got around to now.
I decided to modify it by adding the option to run it from a battery.
According to the processor datasheet, it needs 3.3 V. I planned to power it from a lithium battery. But since the battery voltage ranges from 2.8 to 4.2 V, I needed to bring it down to the required 3.3 V somehow.
There were two options.
1. A low-dropout regulator. Simple, rugged, and compact. But it worked out more expensive (a good ultra-low-dropout regulator doesn't come cheap), and I would only get a voltage range of 3.4–4.2 V.
2. A SEPIC converter. Much more complex and noticeably larger, but it provides 3.3 V across the full 2.8–4.2 V range.
3. A step-up converter to 5 V, followed by the step-down converter already on the board.
That's just not sporting, and it's less efficient.
I decided to go with the second option. To that end, I bought several DC-DC step-up converters and tried converting them to SEPIC in this
review.
Since the conversion experiment was successful, except that the larger board didn't fit very well inside the small router, I decided to make my own board.
But the router itself also needed a way to charge the battery, so I added a charger to the circuit as well.
This is the circuit I ended up with.
TP-link TL-WR702N or my new little helperI laid out a small circuit board based on this circuit. I wanted it to fit within specific dimensions, so the old inductors wouldn't work and I had to buy smaller ones.
I etched a board that included both the converter and the PoE power isolation circuit.
The cameras also need a power source while they're running. For that, you can either use a PowerBank with
12 V, or power them from a PoE switch. I usually use PoE switches. In that case, you just need a simple isolation circuit: power comes from the switch, and the router connects to the camera via the signal lines.
TP-link TL-WR702N or my new little helperSUMIDA CDRH73 series
CDRH73 inductors worked well as smaller replacements.
The other components were scavenged from other boards, including a DC-DC converter board; I had some of them at home.
TP-link TL-WR702N or my new little helperI also bought several types of switches to control the board's power source: battery or mains.
As I mentioned above, I reused some components from DC-DC converter boards. From the larger board, I took the 28 µF capacitors, the IC, and the voltage-divider resistors.
From the smaller boards, I only took the LED.
TP-link TL-WR702N or my new little helperThe assembled board doesn't look very neat, but it's compact. I also miscalculated the diameter of the wire pads a little; that's been fixed in the revised PCB layout.
TP-link TL-WR702N or my new little helperThe board turned out noticeably more compact than the off-the-shelf DC-DC converter, and it has a switch, a charger, two inductors, and an additional filter on the 3.3 V output.
TP-link TL-WR702N or my new little helperI bought a couple of 360 mAh batteries to power the board. I chose ones that would fit, but had to buy two because I figured one wouldn't be enough. They fit perfectly in terms of height.
The LP402245-PCM-LD
LP402245-PCM-LD batteries have protection boards; I bought them locally.
TP-link TL-WR702N or my new little helperThe capacity turned out to be lower than claimed, although I always thought these batteries were pretty good.
TP-Link TL-WR702N or my new little helperThe board worked right away; there was no need to adjust or add anything. I got an output voltage of 3.34 V, which is more than good enough.
TP-Link TL-WR702N or my new little helperNext came the router modification. First, I had to cut the trace from the USB connector to the board's DC-DC converter.
After that, I soldered onto the 3.3 V supply after the converter. The easiest place to solder is directly to the output capacitor leads: negative on the left, positive on the right.
Near the USB connector, I scraped the solder mask off the traces and soldered wires to them, since soldering to the connector pins is very awkward.
TP-Link TL-WR702N or my new little helperI routed the soldered wires to the top side of the router board (the 5 V connection is already on top, and the 3.3 V wire comes through the USB connector opening).
TP-Link TL-WR702N or my new little helperTo install the board, I had to shorten one of the case's posts a little. The rest was straightforward: mark the switch hole from the inside.
TP-Link TL-WR702N or my new little helperThen transfer the mark to the outside and drill, saw, nibble away at it—whatever works for you :)
TP-Link TL-WR702N or my new little helperBut then I hit a major snag: I broke the switch stem.
It had made me a little uneasy from the start, and when I tried to switch it, it gave way and snapped :(
As I mentioned earlier, I bought three small switches of different types. This one was the best fit.
Of the two remaining, one was out immediately because its stem was too short. I had to use the other one, but it needs a noticeably wider hole.
TP-Link TL-WR702N or my new little helperBut once I installed the new switch, I realized I'd actually got an even better result than I'd planned.
The thing is, the board now stays firmly in the case without any fasteners (I had planned to stick it down with thick double-sided tape). Just pop it in and that's it: the board rests against a post in the case and doesn't move around.
TP-Link TL-WR702N or my new little helperHere's the finished assembly with just one battery for now. I laid everything in place to see how it would fit, and it looks as if it had always been there :)
TP-Link TL-WR702N or my new little helperIn the previous review, where I also modified the DC-DC converter, I was asked to check whether the board could run from 2 V and deliver 200 mA at the output.
No, the board reliably maintains a 3.3 V output with an input of 2.14–2.2 V, but if you lower the input any further, the output voltage drops sharply to 1–1.5 V.
More out of curiosity, I measured the current draw at various input voltages. I used the power supply from this
review.
I initially expected a higher current draw, so I bought a pair of batteries. Testing showed that things worked out better than expected, and one battery would have been enough for about an hour of active use.
But since I had already bought the batteries, I decided to install both.
Estimated runtime in this configuration is about 2–2.5 hours.
TP-link TL-WR702N or my new little helperIt was time to put everything back together, but first I had to completely cut off one of the standoffs (it held the board in the case) and part of the USB connector retainer.
The standoff was on the left in the photo, and the retainer on the right; both are marked with arrows.
TP-link TL-WR702N or my new little helperThis is how I managed to “pack” everything inside :) The batteries fit snugly, but I also secured them to the RAM chip with double-sided tape to keep them from shifting inside the case.
TP-link TL-WR702N or my new little helperThere was just one unresolved issue left: the charging indicator LED.
I wouldn't say it's essential, but it would be handy to have.
The case is made of plastic that barely lets any light through. The original LED has a light guide made of clear plastic, and I didn't want to spoil the appearance too much.
A brief digression. The board has a 1.5 kΩ resistor in series with the LED; I specified 1 kΩ in the schematic. You can reduce it to 680 Ω, but it's best not to go lower. The reason is that the LED isn't connected quite as shown in the datasheet.
The correct way is to connect the LED to 5 V, but I couldn't route a trace to 5 V, so I powered it from the battery instead.
The board stops charging when the current drops to 1/10 of the set charging current. I set the charging current to 300 mA so as not to overload the power supply if the battery is charging while the router is running.
If you reduce the LED current-limiting resistor too much, charging may never stop, or may take a very long time to stop, even when the battery is fully charged.
Anyway, I marked out a spot in the cover above the LED and carefully removed some of the plastic, leaving a thin layer.
TP-link TL-WR702N or my new little helperIt isn't very bright, but it's clearly visible, and that was good enough for me. I could make it a little brighter by reducing the resistor further.
TP-link TL-WR702N or my new little helperThe exterior changes are minimal; I only added a power switch.
In the left position, it runs from the battery; in the right position, it runs from the power supply and charges the battery.
The battery charges in both positions, but I don't recommend charging it in the left position, as it will take a very long time or may not charge at all.
TP-link TL-WR702N or my new little helperIt turned out quite neat, though it could have been better. The power cable doesn't get in the way of the switch.
TP-link TL-WR702N or my new little helperAnd that's the end of the modification :)
The result. This solution has already been tested and works fine, though once the image started to lag. I haven't figured out why yet. For the test, I used this
camera at the maximum stream setting…
In practice, it turned out to be very convenient. Just yesterday, we were installing cameras somewhere with absolutely no cell phone coverage. With this setup, there was no problem configuring the camera, even there :)
TP-Link TL-WR702N or my new little helperSo, to sum up.
ProsThe router works. If not brilliantly, then at least well.
There's plenty of free space inside the router.
Sturdy case.
Good packaging
ConsEverything is in Chinese :(
The power supply plug has flat prongs.
My opinion: this is a perfectly decent router. Several months of testing showed that it works reliably. The signal isn't especially strong, but it's quite stable.
I was pleased to find so much free space inside :))
Chinese isn't very convenient—in fact, it's downright inconvenient. But what's worse is that switching it to English isn't easy, if it's even possible at all. A shame, because I liked the hardware itself.
I hope you found this review interesting, and perhaps useful too.
Datasheets, schematic, circuit board.
Download.
The product was provided by the store for review.
