Author Archives: Ian

Breakout boards from Taobao are a mess

via Dangerous Prototypes

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For the last few days I’ve been playing with breakout boards purchased from Taobao. So far it’s been a nightmare.

GY-271 is advertised as a Honeywell HMC5883L 3 axis digital compass. A Bus Pirate address search turned up 0x1A and 0x1B, instead of the HMC5883L’s 0x3C and 0x3D. The chip is actually a “Q”MC5883L, a Chinese-made digital compass with similar features that is not register compatible.

The datasheet for the QMC5883L shows the chip markings as “DA5833”. These markings are visible in nearly every Taobao listing claiming to be a HMC5883L breakout boards. Honeywell’s datasheet doesn’t include chip markings, shame on them.

GY-273 is another HMC5883L breakout board all over Taobao. About half of these are clearly the “Q” type chip. The other half show the Honeywell chip, at least in the photo. After talking with a quasi-trusted vendor I ordered what are supposed to be actual HMC5883L breakouts.

GY-213 is a breakout board sold with a variety of temperature and humidity sensors, including SI701, SHT21, etc. The same color/size/pinout/layout PCB is available from tons of Taobao shops. I ordered a SHT21 version from Youxin, a trusted supplier. The chip appears to be genuine, not the Chinese-made HTU21D, but it seems to be defective in at least two ways.

SHT21

Reading out the configuration register shows 0x3A=00111010, but the power up default should be 000xxx01. At power up the on-chip heater is enabled, which is used for testing and diagnosis. “OTP Reload” is enabled, which is specifically “not recommended for use” by the datasheet.

After setting the correct configuration it was time for further disappointment. Humidity measurement is always around 0xF66A. 114.3% humidity seems unrealistic, even for Shenzhen in the spring.

Dirty terminal sample pack

via Dangerous Prototypes

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Crimp Terminals for Cables

Crimp terminals lock to the end of a wire and attach to an electrical connection such as a screw or terminal block. There are tons of different styles out there, but we found a handful that every Chinese cable manufacturer stocks. This is important because while reels of crimps are cheap, each crimp uses different tooling and manufacturers only buy tooling for the most common crimps.

In the previous post we covered commonly used JST and Molex compatible parts from the Shenzhen markets. These connectors come in two parts: a metal crimp that attaches to the wire, and a plastic crimp housing that holds all the crimps in place. This post looks at common crimp terminals that don’t use a plastic housing. Get the sample kit here, or build your own custom cables here.

Ring terminals

ring-set

These super common crimps attach to a bolt or screw terminal block. Four sizes are super common in the market and all fit a corresponding metric bolt size: 3.2mm (M3 bolt), 4.2mm (M4), 5.2mm (M5), 6.2mm (M6). Smaller and bigger sizes are available, but the crimps are rarely stocked so you’ll generally be on the hook for MOQ if you stray from this safe range.

Our manufacturer recommends 18AWG wire for all crimp terminals.

Spade terminals

spade-set

Spade or fork terminals attach easily to a bolt or screw terminal without fulling removing the screw from the terminal. We only found these in 3.2mm (M3) and 4.2mm (M4) in the market.

These work with common screw terminals and grounding bolts, but we found these really nifty PCB mount connectors (through-hole) with a single screw terminal. The manufacturer has a range with parts numbers from PCB-1 to PCB-14 that vary primarily in the height of the leads. PCB-2 is the most compact and lowest profile version, so we’ve been working with it.

Our manufacturer recommends 18AWG wire for all crimp terminals.

Blade terminals

blade-set

Male and female blade terminals connect cables to board mount connectors AND cables to other cables. Available in multiple sizes, but 2.8, 4.8 and 6.3 are the common.

There are multiple type of terminal blocks for connecting female blade connectors to PCBs or wiring harnesses. We found single PCB mount connectors (through-hole) for use with female blade crimps. The smallest versions (2.8) use 0.5mm thick metal, while the 4.8 and 6.3 version use thicker 0.8mm metal. The two bigger connectors have offset tabs to provide additional stability.

Our manufacturer recommends 18AWG wire for all crimp terminals.

Other crimp terminals

A lot of available crimp terminals are missing from this list: male and female bullet connectors, right angle blade connectors, etc. A reel of these crimps is not expensive, but most cable manufacturers don’t have the proper tooling work with them in their crimping machines. Crimp tools can range from $100 to $1000s, depending on the machine and if the manufacturer has to customize the tools.

If you’re looking to do low volume cheaply, the it’s always best to use what multiple manufacturers and distributors have available in the market.

Insulated covers

All three types of crimp terminals have compatible insulators in multiple colors. We’re not yet equipped to offer these in the dirty cables creator.

Maximum ratings

Please note that we’re unable to provide maximum ratings at this time. Our cable suppliers don’t have datasheets for the common “duff” stuff they’re using, so you’ll need to do the same due diligence on the final cables that you would if buying directly in China yourself.

We’ll need to find our own crimp terminal manufacturer and supply parts to the cable maker ourselves to get properly rated parts.

Touch it yourself: Dirty Terminals Sample Pack v1.0

Buy the kit. Can’t wrap your head around it without getting your hands on these parts? Don’t worry, we’ve got you covered. All these crimp terminals and mating connectors are available in the Dirty Terminal sample pack. Grab it in the store for $4.95.

Dirty Cables: Get your own custom cables

DirtyPCBs

Get cheap custom cables for your project, direct from Huaqiangbei. Use the Dirty Cable creator to drag and drop wires and connectors into a cable and price custom cables from quantity 100.

Taking it further

In the coming weeks we’ll cover coaxial power connectors and LED strip sockets.

Dirty Cables price increases and lead times

via Dangerous Prototypes

DirtyPCBs

Its really hard to convince Huaqiangbei market suppliers to cooperate on a project until you can prove value by making a bunch of orders. Our approach is to guestimate a price at DirtyPCBs, send through a few months of orders, and then ask if they’d like to cooperate with us. Generally this will open doors to closer integration like getting full price lists.

After a few months of running Dirty Cables we looked at our overall order history. On 75% of orders we lost anywhere from $5 to $500. This was totally expected and part of convincing suppliers to give us full pricing details.

Our current supplier makes outstanding cables, but getting a quote is still like pulling teeth and takes ages. They also seem completely uninterested in providing a full price list. We’re in the market today shopping for a new supplier, but in the meantime prices on most connectors have been doubled or more based estimates from the first few months of data. It would also be fair to say lead time is currently 10-20 days, more on large or complicated orders.

Since a lot of the loss/expense is in the low volume orders of 100 cables, we need to compensate with bigger discounts on high volume orders. Connector prices are easy to update in the back end, but volume discounts require a site update that will come towards the beginning of next week. If you’re placing a large order and think the price is too high, please contact us for a more accurate quote.

DIRTY CABLES: Cheap custom cables available now

via Dangerous Prototypes

DirtyPCBs

Dirty Cables is a drag and drop cable builder that gives you access to cheap custom cable services from China. Build a custom cable, get an instant quote, and checkout. Your custom cables should ship in 3 to 7 work days.

Huaqiangbei is full of cheap custom cable vendors with a big pile of samples on their booth. We tried to put the pile online so you can get cheap cables without making a trip to China!

cable-pile-2

We excavated the cable sample piles to see which connectors are common, cheap and readily available in the Chinese market. We bought bundles of everything and identified 17 common cable-to-cable and cable-to-board connector families to add to Dirty Cables. Read more about the different cable families here.

Cables are probably best understood by touching them yourself, so we put together a Dirty Cables Sample Kit that includes examples of each cable and connector. The kit is available in the store for $9.95.

In the coming weeks we’ll document a few more common and cheap connectors that didn’t quite fit in the first sample kit:

  • Crimp terminals: ring and spade ( M3/3.2mm, M4/4.2mm, M5/5.2mm, M6/6.2mm), two-part blades (2.8mm, 4.8mm, 6.3mm)
  • Coaxial power connectors (5.5×2.1mm, various)
  • LED strip connectors (3528/8mm, 5050/10mm, etc)

Dirty Cables is highly experimental. If pricing seems way off, if you find bugs, or if we’re missing your favorite connectors, please give us a shout in the comments or through the contact form.

DIRTY CABLES: Cheap custom cables available now

via Dangerous Prototypes

DirtyPCBs

Dirty Cables is a drag and drop cable builder that gives you access to cheap custom cable services from China. Build a custom cable, get an instant quote, and checkout. Your custom cables should ship in 3 to 7 work days.

Huaqiangbei is full of cheap custom cable vendors with a big pile of samples on their booth. We tried to put the pile online so you can get cheap cables without making a trip to China!

cable-pile-2

We excavated the cable sample piles to see which connectors are common, cheap and readily available in the Chinese market. We bought bundles of everything and identified 17 common cable-to-cable and cable-to-board connector families to add to Dirty Cables. Read more about the different cable families here.

Cables are probably best understood by touching them yourself, so we put together a Dirty Cables Sample Kit that includes examples of each cable and connector. The kit is available in the store for $9.95.

In the coming weeks we’ll document a few more common and cheap connectors that didn’t quite fit in the first sample kit:

  • Crimp terminals: ring and spade ( M3/3.2mm, M4/4.2mm, M5/5.2mm, M6/6.2mm), two-part blades (2.8mm, 4.8mm, 6.3mm)
  • Coaxial power connectors (5.5×2.1mm, various)
  • LED strip connectors (3528/8mm, 5050/10mm, etc)

Dirty Cables is highly experimental. If pricing seems way off, if you find bugs, or if we’re missing your favorite connectors, please give us a shout in the comments or through the contact form.

How Scotty made his own iPhone in China

via Dangerous Prototypes

Over the past two months we’ve been super excited to follow Scotty’s adventure recycling/refurbishing an iPhone 6S in the used cell phone market just south of Huaqiangbei, Shenzhen, China. Scotty finds all the bits and pieces from various sellers and then follows the iFixit instructions, backwards, to build his own recycled franken-phone.

Despite living in the market and running six hacker camps, it was still not clear to us exactly what goes on in the used cell phone markets. This video blows that open and exposes the brisk trade in recycled iPhone parts here in Shenzhen.

Along with This is Not Rocket Science, Scotty also took us on a three day phone recycling expedition earlier this month. Watch his channel for more videos and clips soon!