First Impressions of DX SSC P7 Bike Light- Mtbr.com
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  1. #1
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    First Impressions of DX SSC P7 Bike Light

    Got mine in the mail today. Only took a week, but I splurged and got EMS shipping. I was kind of surprised they got it shipped that way, I'd read in some forums on DX you couldn't ship Li-Ion batteries via EMS.

    I bought one of these because I've been planning to sell an MCE based light, kind of modeled after some of Troutie's and Scar's designs. Even designed my own driver. I figured I'd wait to see if these were any good before continuing. There is no way I can compete with a price of $80.

    Right out of the box, looks pretty nice (darn or yeah, depends on your viewpoint). The housing is aluminum (I'm pretty sure), not plastic. Looks very well machined, and decently anodized. The O-rings included with the light are almost impossible to hook on the base, especially the smaller fatter one.

    Pretty easy to take apart. And that's really a problem. There is very minimal thermal paste in mine, like none.The LED star is not even epoxied to the base that holds it. There was a faint trace of some kind of grease on the back, may have been thermal. When I put it back together I'll be using lots of artica alumina epoxy. I'll post some pictures as I do this if anybody else want's to make one of these things work.

    The base that holds the star and driver is made of a piece of aluminum. The driver is soldered to a brass ring that force fits into the bottom of the base. Just stick a screwdriver in the obvious slot and you can pry both pieces apart.

    To take the whole thing apart, it's probably easiest to unsolder the connections right at the LED.

    Whoever did the machining did no deburring. There were visible pieces of aluminum dust all over the inside of the base. That seems like a recipe for sudden failure as you bounce downhill and a piece of aluminum falls off the base and shorts out some crucial bit of circuitry in the driver.

    I'm going to put the driver thru it's paces sometime tonight or tomorrow.

    Looking at the top side:

    Looks like a buck with the inductor, current sense resistors and diode on the plus side of the supply. The switching looks like it is done by an 8 pin soic (numbers sanded off) and some kind of small 6 pin part (I'm guessing it's the switcher and the soic is an n-channel mosfet) between the current sense resistors and the soic. The sense resistors are in parallel and are .1 and .5 ohms (so something like .0833 for a sense resistor). They look like 805 smt parts. I would guess they run real hot. The 6 pin chip looks like it's labeled 5241 and maybe one more digit.

    Looking at the bottom side:

    There's a micro, an 8 pin soic. I'm guessing a PIC, will know more after I buzz out the circuit. There's some kind of regulator. A couple of LEDs, one red, one green. There's a pushbutton, not a clicky, so this thing probably leaves the micro running even when it's "off". I'll measure vampire current tonight.

    More to follow, time for dinner.

    Opened the battery pack. It's as you expect4 18650s in a 2s2p configuration. There does appear to be a protection board of some sort, may even be a balance used when charging (there's a wire that runs to where the 2 sets of 2p join). I need to look at it further.

    Mark
    Last edited by [email protected]; 06-01-2009 at 04:58 PM.

  2. #2
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    Dude been running a P7 on the bars for about 1 year already here, maybe longer

    Good Torches though!!

    I've got a 400Lumen MC-E on my bars aswell all the bar light you'll ever need, well for the time being

  3. #3
    aka RossC
    Reputation: ocean breathes salty's Avatar
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    Thanks for the review. I was half thinking about getting one for Mrs Salty to commute with but now I am not so sure....

  4. #4
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    [email protected], Nice little review. So $80 including postage + $10 for some thermal paste and you could maybe have a decent light.

    Makes me wonder how the chinese can afford to eat.

  5. #5
    www.hahntronix.com
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    Well you need to do a bit of soldering as well. And once you've opened it up, you might as well put on some thicker wire than the anemic 22 guage they have running from the battery. Which probably means drilling a couple wholes out the back (if there's clearance).

    The other part that worries me is the driver. I designed a couple of P7 drivers and eventually gave up and switched to working with MCEs. At 2.4 amps things get pretty hot, pretty fast. Especially if you are running 1/2 a watt thru some teensy 805 current sense resistors. Those things will get real warm if you run on high for more a couple of minutes. Now that I have everything apart, I'm going to run the driver thru it's paces and see if it overheats badly.

    Mark

  6. #6
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    [email protected] -- Thanks for the review!

    Keep us posted...

  7. #7
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    Doh!!! Sorry this is the new cheap bike light your reviewing.

    Abit of TLC required (} thermal paste ) and other than that it all sounds good.


    Sorry

  8. #8
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    Hey mhahn, how did the driver fair? I've been thinking about ordering one of these lights and wanted to hear what else you thought.
    Thanks for the above review

  9. #9
    www.hahntronix.com
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    Sorry, I haven't completed my electrical tests yet, but I have a more few observations.

    The circuit board in the battery pack looks like a simple over-volt / under-volt circuit. There are 2 larger 8 pin soics that are mosfets (TPC8209). There is another smaller 8 pin soic with a handful of parts around it (M348292D). I haven't been able to find out what this part is. It might regulate charging, the extra wire running to the middle of the 2p2s battery pack is what gives me hope it might. But more likely it is just an under-volt / over-volt detector.

    There does not appear to be a fuse on the battery pack! And there are no resistors near the M348292D that could be current sense resistors their values are all to large. My guess is there is no overcurrent protection in the battery pack. Anybody want to short theirs out and prove me wrong? If you try it, do it outdoors. And take pictures.

    The soldering quality on the battery pack board is pretty good. The layout has a nice crisp machine generated look to it. I'd guess the company building the lites is buying the battery board from another supplier.

    The charger looks like a simple power supply. It has a single sided thru-hole printed circuit board. Looks like it was hand soldered. There's no IC on the board at all. You would need one to would handle the standard lithium ion charging algorithm. It's just a transformer, 5 transistors, 5 diodes, and a handful of other 2 terminal parts (resistors and capacitors). It may be a switching supply, but without an IC is is unlikely to be very efficient or well regulated. It has a fuse covered in heatshrink (soldered in place, so don't blow it). I suspect it just provides 1.8 amps of current at about 8.5 volts, till the battery pack over-voltage circuit removes the batteries from the circuit. This is not a great way to charge the batteries, but it is probably the technique a lot of cheap Chinese chargers use. It will probably shorten the life of the batteries. I would charge the battery pack outdoors in a metal box.

    On the driver board I found what the driver chip is: http://www.micro-bridge.com/data/semi-micro/SM5241.pdf Anybody fluent in Chinese?

    As I expected the current sense resistors on the driver board run really hot. I haven't tried measuring temperature with anything but a fingertip but they register as TDH (Too Damn Hot ). My guess is that since you are running .4 watts thru a quarter watt resistor (or given the size it might be an eighth watt), at least one of the sense resistors will fail over time, and your lite will get suddenly dim. I would recommend putting in higher current resistors for the ones labeled R03 and R04. It looks like you can fit a 1206 sized resistor package in place of the 0803 sized ones they used in my lite. If you put in two .18 ohm resistors (digikey part: http://search.digikey.com/scripts/Dk...L16R.18FCT-ND), your light wouldn't get quite as bright, but each sense resistor would only need to dissipate .22 watts. I'll probably try this at some point and report my results.

    The micro on the driver board is not a PIC or AVR. It has a pretty weird pinout. I'm guessing modding the board so it has just 2 levels without the annoying strobe isn't going to be easy to do.

    I couldn't find anything on the driver board that looks like a temperature sensor. So I'm guessing there is no heat sensing that will dim the LED when it overheats. There might be a temp sensor built into the micro, but given the poor thermal contact between the LED and the driver it won't be much use.

    I wouldn't recommend this as a lite to anybody unless they are capable of modding it to improve the heat dissipation (improve thermal contact between LED and case) and are handy with a soldering iron. It will probably work great for a few days or weeks, but the LED is going to overheat and die at some point.

    Later this week, I'll post some pictures of the mods I want to do, and hopefully report back that the patient survived.

    Mark

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