Finding the cheapest board house

PCB

The prices for custom made circuit boards has never been cheaper, but surprisingly we’ve never seen a comparison of prices between the major board houses. [Brad] took the time to dig in to the price of 10 boards manufactured by Seeed Studios, OHS Park, and BatchPCB. He made some pretty graphs and also answered the question of where you can get your circuits made cheaply.

[Brad] got the prices for boards up to 20 cm x 20 cm from Seeed Studio’s Fusion PCB service, OSH Park, and BatchPCB. These results were graphed with Octave and showed some rather surprising results.

For boards over 20 cm2, the cheapest option is Seeed Studios. In fact, the price difference between Seeed and the other board houses for the maximum sized board is impressive; a 400 cm2 board from Seeed costs $150, while the same board from OSH Park is close to $1000.

Of course most boards are much smaller, so the bottom line is  for boards less than 20 cm2, your best bet is to go with OHS Park. If you don’t care when your boards arrive, or you need more than 10 or so, Seeed is the way to go. As far as the quality of the boards go, OSH Park is up there at the top as well.

Ask Hackaday: What’s an easy way to build a potentiometer for a soldering iron?

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[Lee] wrote in to share the work he’s done in building a controller for his soldering iron. The idea started when he was working with an ATX power supply. He figured if it works as a makeshift bench supply perhaps he could use it as the source for an adjustable iron. To get around the built-in short-circuit protection he needed a potentiometer to limit the current while allowing for adjustments. His first circuit used a resistor salvaged from an AT supply and a trimpot from some computer speakers. That melted rather quickly as the pot was not power rated.

This is a picture of his next attempt. He built his own potentiometer. It uses the center conductor from some coaxial cable wrapped around the plastic frame of an old cooling fan. Once the wire was in place he sanded down the insulation on top to expose the conductor. The sweeper is a piece of solid core wire which pivots to connect to the coil in different places. It works, and so far he’s managed to adjust a 5V rail between 5A and 20A.

How would you make this system more robust? Short of buying a trimpot with a higher power rating, do you think this is the easy way to build a soldering iron controller? Let us know by leaving your thoughts in the comments.

[Read more...]

MIT Media Lab’s month in Shenzhen

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When you’ve got a month worth of blog postings it’s pretty difficult to choose one photograph that sums it all up. This one shows the tour group from MIT Media Lab in ESD garb ready for their tour of Okano SMT and Speaker Factory. It was part of a tour of Shenzhen aimed at bringing graduate students up to speed on what it means to manufacture products in the city. Luckily, Freaklabs member [Akiba] was one of the staff members of the program and blogged extensively about the experience. At first glance his page full of post abstracts looks really boring, but click through because both his recount and the commented images associated with each day are fun and fascinating ways to tag along with the group.

If you’re really good with faces you can pick [Bunnie Huang] out of the lineup above (he’s the third from the right). He had the original idea for the program and brought aboard a few others to help make the thing a success. The group toured a wide range of factories and parts markets in the city. This included your traditional electronics manufacturing venues but there was even a side trip to a diaper and feminine napkin plant to see the non-electronic factories in operation. In addition to tours there were lectures by industry members like HAXLR8R, a group that specializes in helping start-ups navigate the manufacturing jungle.

A look at the (now patched) security of [Kim Dotcom's] MEGA cloud storage service

mega-cloud-storage-security

MEGA is a new, encrypted cloud storage system founded by [Kim Dotcom] of MegaUpload fame. They’re selling privacy in that the company won’t have the means to decrypt the data stored by users of its service. As with any software project, their developers are rapidly making improvements to the user interface and secure underpinnings. But it’s fun when we get some insight about possible security problems. It sounds like the issue [Marcan] wrote about has been fixed, but we still had a great time reading his post.

The article focuses on the hashes that the website uses to validate data being sucked in from non-SSL sources using some JavaScript. Those insecure sources are a CDN so this type of verification is necessary to make sure that the third-party network hasn’t been compromised as part of an attack on the MEGA site. The particular security issue came when the hashes were generated using CBC-MAC. [Marcan] asserts that this protocol is not adequate for the application it’s being used for and goes on to post a proof-of-concept on how the messages can be forged while retaining a hash that will validate as authentic.

[Thanks Christian]

Messenger bag LED matrix keeps bikers safe at night

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Get a little more exposure than one under-saddle bike light can provide by building your own LED enabled messenger bag. It looks like the bag itself was fabricated from scratch by [Andrew Maxwell-Parish] rather than altering an existing bag. He had a few goals for the project, the most interesting of which was to make the electronics removable. His reasoning for this is so he can get the bag past security at the airport.

The design is quite simple, there’s a large flap which is attached at the top of the bag and has a couple of clips at the bottom to keep ti closed. On the inside of the flap he sewed a snap system which holds one piece of material on which all of the electronics are attached. The Lilypad system is used (it looks like the original hardware and not the FLORA upgrade). The main unit is sewn to one side, while the Charlieplex LED matrix was attached in a grid centered on the flap. The lights shine through the orange fabric, keeping them fairly safe from the weather and giving them a reddish hue.

If you’re looking for a few more features check out this GPS enabled messenger bag.

Help hackaday buy our own 3D printer UPDATED!

beggars

UPDATE: We’re getting a LulzBot thanks to [Jeff Moe].

ALL DONATIONS ARE BEING REFUNDED. YOU WILL STILL RECEIVE YOUR STICKERS.

We’ve held out for far too long. Hackaday now needs a 3D printer.   We get emails all the time asking why we don’t have a donate button. Well, we’re kind of stubborn and would rather just do with what we have. Unfortunately this hasn’t gotten us very far in the 3d printer department.

We have a few projects in mind that could really utilize a 3d printer, namely building custom game controllers for children with special physical needs.

If you have any interest in helping us get a 3D printer for Hackaday, read on. Otherwise, carry on with your day.

[Read more...]

Adapting the Nexus 7 for a double DIN car dashboard opening

making-nexus-7-fit-in-double-DIN-dashboard

It turns out that the Nexus 7 Android tablet is the perfect size to fit in a double DIN opening. DIN is the form factor of a single CD head unit for an automobile. Many models have room for a double DIN, which is defined as 4″ high by 7″ wide. Once [Meta James] figured out that the dashboard bezel for his Subaru framed the Nexus 7 perfectly he set out to fabricate the mounting system for an in-dash tablet installation.

Unlike a lot of these dashboard tablet installs, [James] didn’t need any Bondo, sanding, or painting to get things to look right. Like we mentioned, the bezel is a perfect fit so his alterations are hidden behind the tablet itself. He removed the stock head unit and ordered a DIN adapter kit to get the black bracket plate seen above. He built an acrylic box the same size as a double DIN head unit, then mounted the plates to the sides and a Nexus 7 case to the front. This holds the tablet in firmly, lets him mount the entire assembly using the factory mounting points, and leaves plenty of room for the cabling that connects the device to the car. Since he already had a hands-free phone system he just uses that to amplify the audio fed to it via Bluetooth.

[via Reddit]

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