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Visit to Shenzhen, Day 2 — Hua Qiang Bei

Sep 4th, 2013 by ray

Continuing my last post about this week’s trip to ShenZhen, today’s agenda is to visit Hua Qiang Bei (HQB) — the largest electronics market in the world. HQB is located close to the center of the city. The name literally means the north of the Hua Qiang street. The area spans several big buildings, each of which is full of counters and booths selling all sorts of electronics components and gadgets.

After coming out of the metro HQB station, the first building that came into my eyes is this one:

The banner says Hua Qiang Electronics World. Sounds like a place I should be, so I headed right in. Turns out this section of the building is mostly selling laptops, mobile phones, and commercial electronics gadgets. A bit disappointing. However, I discovered that the top two floors are dedicated to LEDs, which is one of the things I am looking for. As soon as I went up, I was faced with a sea of LEDs. There are just too many of them: some are for home lighting, illumination, some are for decoration. Many of them are color LEDs, displaying fancy moving patterns. It’s really awesome. Most sellers here are only interested in customers buying in large quantity. So if you tell them you are buying less than a hundred, they tend to lose interest right away and give you the ‘go away’ look. Some sellers do have the patience of talking to you and listening to what you do. I would rather patron these sellers 🙂

One of the LEDs I was looking for is of type WS2812, which is used by Adafruit on their Neo Pixels. This type of LED has a built-in IC which allows you to set the brightness of each color separately, and most amazingly it takes only one data pin. You can also cascade multiple LEDs. The data is sent in like shift register, and it gets latched on each LED. This is really a very smart design: with only one data pin, you get to control mutiple independent LEDs, and it requires minimum mcu cycle to operate. Many sellers that carry this product sell them in the form of fully assembled tapes of LEDs; a few do sell just the LEDs, at a price of about $110 for a bag of 1000. Sounds like a competitive price. Short of a reference price, I decided to look around and come back to buy when I feel ready.

The next stop is the ‘Q’ section of the building, which is dedicated to all electronics components. When I walked into this section, it feels absolutely like a heaven for electronics lovers. There are endless counters that sell all sorts of components that you can think of.

When I say ‘endless’, there is no exaggeration: standing at any point of the floor, you simply cannot see the end. It’s very easy to get disoriented. Also, there are multiple floors, each of which has a slightly different focus. The picture above on the right shows a counter that sells switches. Thinking of those times you spent on trying to find a Digikey part that fits your need? Here you can take out a real sample right at the counter and check it out in your hand.

I am curious how to choose which seller to buy from — since there are so many of them, the choice almost feels random. One thing I learned is that you shouldn’t feel rushed to buy: go around and compare different sellers before you make up your mind. Even at this low profit margin, there are still noticeable differences in price. Of course quality is also very important — often you can get a good idea by talking to the seller, and see if they are knowledgeable and professional. I tend to patron sellers who are willing to engage in a conversation and interested in knowing what I do.

It’s very easy to get lost and spend hours and hours here in the market. Moving to a different section in the building, I came across a floor which sells all sorts of cables, connectors, power adapters, terminal blocks etc. If you intend to buy a large enough quantity, you can also ask the seller to customize the product. Most things can be tailored to order. For example, I asked about 24VAC power transformers, and one seller told me depending on my need, they can customize the winding of the transformer and change the plug to any type of my choice. Wow, this is simply awesome 🙂 I was about to head to my next stop, which is the Sai Ge Electronics Market, and I ran out of time. So I will have to come back and visit again.

At the end of the day, I didn’t buy a whole lot: my goal was to do some initial sight-seeing in order to get an idea of where to focus my attention when I come back a couple of days later. Below is what I bought though: two bags of 1K self-flashing RGB leds, one bag of 1K SMD slide switches, two bags of 200 testing probes, and a few mini relays. With a total spending of less than $100, it’s a real bargain. Can’t complain at all 🙂

After I was done with HQB, my friend brought me to the swimming pool at the ShenZhen Bay Sports Center. This is undoubtedly the largest pool I’ve ever swimmed in, and a good way to end today. So long for today’s report. Will keep blogging tomorrow!

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Visit to Shenzhen, Day 1 — SeeedStudio

Sep 3rd, 2013 by ray

This week I am on a business trip to Shenzhen — the city with the largest electronics markets in the world. My plan is to visit several studios / factories and the of course the electronic markets here, and also some of my old friends. I will try to document my trip as much as I can.

Shenzhen is located at the very south of China — it’s right above Hong Kong. The weather at this season is usually very hot and humid. Fortunately it has been raining for the past couple of days so it’s not as toasting as it normally is. The image above on the right is the look of the city from my hotel window. There is an electronics market right across the street on the other side 🙂

One of the challenges of traveling in China is that a lot of external websites are blocked by the Chinese government. For example, Facebook, Twitter, Gmail, NYTimes. I was able to use a private VPN to get around with it, but the data transfer speed is really slow. On the plus side, you have access to a wide variety of inexpensive food, which is hugely attractive to a gourmet traveler like me 🙂

On the first day, I visited SeeedStudio, the company that is currently in charge of manufacturing the fully assembled OpenSprinkler 2.0. SeeedStudio is well known in the open-source hardware community, and they have been growing at amazing speed in the past couple of years. I have been looking forward to this visit for a while.

The building where SeeedStudio is located at looks very, short of finding the right word, non-technical, which made me feel that I’ve walked into the wrong place. But as soon as I found their main lobby, I was reassured. On close look, the back wall is made of hundreds of circuit boards painted in white. Very interesting.

Here is a picture of the ‘innovation corner’ and also the marketing / PR section of the studio.

The main agenda today was to discuss the design of a paper box and a printed user manual for OpenSprinkler, making a mold for the OpenSprinkler Zone Expansion board, and designing a laser cut enclosure for OpenSprinkler Pi. The meeting was quite productive: I talked with the product manager, an enclosure engineer, and an electronics engineer for several hours. Things got started moving right away. Among the electronics discussions, we covered several potential improvements to the current OpenSprinkler circuit, including preventing users from damaging the circuit by inserting the power to the wrong terminal port, automatic detection of defective solenoids, adding built-in WiFi etc. I felt very excited to start prototyping these ideas right away.

After the meeting, the product manager gave me a short tour of the studio. The top floor is where the offices and meeting rooms are located. The bottom floor is where the production pipeline is.

Here are pictures of the soldering / assembly area, and the SMT pick and place machine.

Next, the laser cutter and a testing area where engineers were testing a brain wave (EGG) controlled drones. Hmm, very impressive!

Finally, here are two bins of assembled and tested OpenSprinklers. It really pleases my mind to see these lovely OpenSprinklers 🙂

So that’s all for my report of Day 1. My next stop is Hua Qiang Bei (???), where you can find almost any electronic component you can think of right at the counters. Looking forward to it!

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New Rayshobby Shop Homepage Available

Aug 16th, 2013 by ray

This is a quick heads-up that the new Rayshobby Shop Homepage is now available. The new page design is based on OpenCart, a popular free and open-source shopping cart software. It is fairly straightforward to set up, although I did spend quite some time creating nice looking graphics, including banners, product images, and product pages. The end result is satisfying. The shop page now looks much more professional with a load of new features. Take a look at these snapshots first:

Before I started, I took a look at several options, including WooCommerce for WordPress, OpenCart, ZenCart etc. WooCommerce has the advantage that it integrates seamlessly with your WordPress blog. But it requires a theme that’s compatible with WooCommerce. Since I have an existing WordPress blog, I tried a few themes with WooCommerce support, and they don’t look that great: the images and formatting all become wacky. To fix them will require a lot of changes. So I’ve decided not to go that route. Regarding OpenCart and ZenCart, they both look great, I think OpenCart looks a bit simpler to set up and the design is more minimalist, so that became my pick in the end.

With OpenCart, it’s now a lot easier to add new products and keep them organized. Also, features like showing related products, applying coupons, comparing different products, managing user accounts, providing different payment options are automatically supported. Definitely a big step forward :). I have also added the distributor page to show current official distributors of OpenSprinkler products.

Of course, since this is a new system, I won’t be surprised if I’ve left some glitches. I will keep my fingers crossed and see how things go. If you see any problem or issue, feel free to let me know and I will get them fixed as quickly as I can. Thanks!

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RI Mini Maker Faire Pictures

Aug 12th, 2013 by ray

Yesterday we went to the RI Mini Maker Faire in Providence. I came back around midnight last night, feeling quite tired. It was a fun trip, and the first time that I went there as a maker. The faire was co-located with the Foo Fest, so even though its size is nowhere comparable to the Bay Area Maker Faire and New York Maker Faire, there were still a decent number of people. We had a single and fairly small table to showcase everything. As you can see from the pictures below, the table was very crowded, but we managed to lay out everything I wanted to show, and the promotional materials as well 🙂

As in previous Maker Faires, the most fun and rewarding part of the experience is that I get to talk to a lot of different people, explain to them how electronic gadgets work, get them excited about electronics, answer their questions, and hear their innovation ideas and solutions. I had two students, Kim and Cheni, who kindly offered their help, so I got to spend more time talking to people.

One tip I learned from the Bay Area Maker Faire earlier this year is that everyone is really excited about blinking LEDs. I know, it sounds trivial, but really, everyone loves it. Last time I just accidentally packed a hundred self-flashing and RGB color LEDs, together with coin batteries in my baggage. While setting up the table, an idea popped up in my mind that we can distribute them as free gifts at the faire. They are really cheap, so I don’t mind giving them away. What I didn’t foresee was how popular this was: the one hundred packets were gone almost in no time.

So this time, I am better prepared: I brought a bag of one thousand self-flashing and RGB color LEDs, together with one thousand batteries! We printed instructions so people can learn how to make an LED throwie on their own (basically sandwiching a coin battery in between the two legs of an LED). We distributed these as free gift to people, but told them it’s only free if they make one themselves (instead of taking away our demos 🙂 ) This was a huge success: I estimated that we gave away at least 250 of these. Many people passing by the table saw this and were eager to give it a try. Kids especially love these. Kim and Cheni were busy cutting tape and helping others learn to build their LED throwies. It’s really rewarding to see something so easy to learn can get people to excited, and it’s also fun to see how people were teaching each other at the table, and bringing their own friends to learn how to build these. Perhaps to some this will motivate them to explore the world of electronics. Then I will feel I have fulfilled my education mission a little bit 🙂

Posted in Maker Faire, Wearable | Comments Off

Announcing AASaver 2.0 (with USB and LiPo charging)

Aug 11th, 2013 by ray

Three months after its first prototype version, I am glad to announce that the long-awaited AASaver 2.0 has finally become available! In case you haven’t seen the first version of AASaver: it is basically a versatile boost converter that takes two AA (or AAA) batteries and bumps them to 5V so you can use it to power flashlight LEDs, or use it for breadboard experiments. The nice thing is that since it’s based on an efficient boost converter chip that has low start-up voltage, it can work with both new and used batteries. Even if the batteries can no longer work in other devices, like remote control, electronic toys, you can still use the AASaver to light up LEDs and run circuit board experiments for a long time. It’s a great way to harvest the remaining energy (or in layman’s term, suck the remaining juice) in your ‘dead’ AA batteries 🙂

The New Design

AASaver 2.0 is a completely redesigned circuit from its 1.x version. Here is a list of new changes:

Added USB port, which allows charging of USB devices such as mobile phones, MP3 players etc. To support up to 500mA charging current, the booster converter is changed to use NCP1450A, an upgrade from the previous MCP1640.
Added lithium battery charger (based on MCP73831), which allows charging of lithium polymer (LiPo) batteries from AA batteries. There is an on-board LiPo battery jack, and an SMT pot (trimmer) to provide adjustable charging current.
There is also an input LiPo jack, so the circuit can take source either from AA batteries or external LiPo battery. There is a good reason to provide this functionality, as explained below.
The original battery clips are changed to a plastic battery holder, which is mounted with screws on the back of the component side. This frees a lot of room on the component side, which in turn reduces the PCB size.
The breadboard pin headers are now changed to the battery holder side. The AASaver now takes much less space when plugged into breadboard. An additional pair of pinouts are also added to fit breadboards with extended width.
It’s also possible to use the circuit for solar charging, and charging LiPo battery from external USB port.

In sum, this version preserves the same basic functionality as before, which is to take two AA (or AAA) batteries and serve dual functions as an LED flashlight and breadboard power supply. But it also has a lot of new features and improved usability, most of which were adopted from user suggestions on the original version. Here is a quick summary of the spec:

Power Source: two AA/AAA batteries, or external 3.7V LiPo battery (selecctable by an on-board switch). Can also be modified to work with a single battery, or with a solar cell.
Power Output: any of the following: flashlight LEDs (seletable by a switch), breadboard pin headers, USB, or LiPo charger. The LiPo charging current is adjustable from 10mA to 200mA through an on-board trimmer.
Output Voltage: 5V up to 500mA.

Here is an annotated diagram for the various on-board components:

Schematic and Board Design

Acknowledgement: the USB charging circuit, particularly the D+/D- line voltages, references the design of the MintyBoost by Lady Ada. Check the details about USB charging therein.

Technically AASaver 2.0 is different from the MintyBoost in that 1) it uses a different boost converter chip (NCP1450A vs. LT1302); 2) it has a built-in LiPo charger; 3) it uses SMT components and is mostly assembled. Also, AASaver is designed to be versatile and serve multiple functions, including LED flashlights, breadboard power supply, USB charging, and LiPo charging. Its primary goal is to make use of old batteries (hence the name AASaver 🙂 ).

The Kit

A limited number of the AASaver 2.0 kits are now available on Rayshobby Shop. More will become available in the upcoming weeks. Included in the kit are one assembled and tested AASaver 2.0 circuit board, battery holder, two pin headers, two bright flashlight LEDs, a power switch, two screws and nuts.

Assembly and Usage Instructions

Although the circuit board is mostly assembled, it does require a few simply assembly and soldering steps to get it fully functional. If you’d rather not assemble and solder anything, you can order a completely assembled AASaver at additional cost. The instructions are posted below with high resolution images. These instructions will soon be posted on the AASaver homepage.

Step 1. Attach the Battery Holder

Use the two screws and nuts to fix the battery holder at the back of the PCB. Make sure that the battery holder wires are close to the side with the AA/LiPo Source Selector (i.e. the opposite side of the USB port).

Next, cut the battery holder wires to about 1 to 2 inches long (don’t cut it too short, or otherwise you will have difficulty soldering it later). Then use a wire stripper to strip the lead, and then insert the wires to the PCB holes and solder them. Make sure that the red wire goes into the hole marked ‘+’, because this is the positive wire. Double check yours with the image on the right below.

If you want, you can use a little bit of hot glue to fix the wires in place. This is not required, but is helpful as the wires are very thin and are prone to breaking if you wiggle them too much.

Step 2. (Optional) Solder the Breadboard Pin Headers and LEDs

Now you need to solder the breadboard pin headers and flashlight LEDs. NOTE: these steps are optional, and depends on what you want the AASaver for. If you don’t need it to run breadboard experiments, you don’t need to solder the pin headers (or you can always solder them later).

To solder the pin headers, first insert the two pin headers towards the end of a breadboard. This will help fixing them in place during soldering. Next, align the PCB holes on the AASaver with the pin headers. The height of the pin headers are designed to match the height of the battery holder, so if everything is correct, the battery holder should sit flat on the same surface with the breadboard. Note that this only works if the pin headers are inserted towards the end of a breadboard — if they are inserted in the middle of a breadboard, the battery holders will sit on top of the breadboard and this won’t work.

Also note that on the left side there is an additional pair of VCC-GND pin holes. These are designed for breadboards with extended width. So if your breadboard is wider than the one shown in the picture below, use the extended pair of pin holes.

Next, to solder the flashlight LEDs, first insert the LEDs to the LED pin holes. These pin holes are located on the same side as the USB port. Make sure the longer lead of the LED goes into the hole marked ‘+’, as the picture below shows. Then gently bend the LED to 90 degrees, and solder the two leads. You can decide how long the LED should stick out of the circuit board, but in general, keep the LED close to the circuit board so that it doesn’t get accidentally bent. Once the LED is soldered in place, remember to cut the excessive leads. Follow the same process to solder the other LED.

Now the AASaver is completely assembled! Below are the usage instructions.

Step 3. Power it On and Flashlight LEDs

Pop in two AA batteries. Make sure you insert them in the correct orientation. Then turn on the power switch. The red Power Indicator LED should light up. If not, check the Source Selector Switch, and make sure it’s turned to ‘AA’ (instead of LiPo In). The Source Selector allows you to select either AA or LiPo as the power source.

Next, turn Flash LED switch to ‘On’, and the two flashlight LEDs should light up. These are two bright flashlight LEDs, which work really well in the dark.

Note that the battery holder also sort of works for AAA batteries, although the contact is not very reliable. So if you want to pop in AAA batteries, try to use a small piece of aluminum foil to fill the gap between the AAA battery with the battery clips inside the holder. This should make it work perfectly.

Step 4. Use it as BreadBoard Power Supply

AASaver is also designed to function as a breadboard power supply. It provides regulated 5V, which is great for many circuit board experiments. To use this function, simply plug the AASaver (with pin headers down) into a breadboard. Note that unlike the AASaver 1.x, the body of the AASaver 2.0 will stay out of the breadboard, so this gives you more room on the breadboard.

Step 5. USB Charging

This is probably the most exciting new feature of the AASaver 2.0: you can now use it to charge USB devices. There is a built-in USB port that fits most standard USB cables. use it to charge your mobile phones, MP3 players, or anything that can charge through the USB port.

Using a fresh pair of batteries, the circuit can provide up to 500mA charging current @ 5V output, which is sufficient for most USB devices. Also, empirical results show that with a fresh pair of batteries, you can charge the iPhone and the Samsung Galaxy S3 phone up to 20% to 25%. This is not a whole lot, but is good enough as an emergency charger, since AA batteries are really easy to get at convenience stores.

Now, there is a tricky question: since the hallmark of the AASaver is to save old AA batteries, can I use old or even almost ‘dead’ AA batteries for USB charging? The answer is mostly NO. Well, there is no magic: most USB devices require a certain amount of charging current in order to charge properly. Mobile phones are particularly power hungry. To provide 100mA @ 5V output, the AA batteries need to output at least (100mA x 5V) = 0.5 Watt power, and usually more to account for the non-perfect efficiency of the boost converter. Depending on the battery condition, you may or may not be able to draw that much power from a pair of AA batteries — for fresh batteries, no problem; for close to depleted batteries, almost certainly no. Technically, the problem with old batteries is that as soon as you start to draw higher current, the voltage of the battery will drop, and so the boost converter will start sucking more current from it, causing the voltage to drop further. At some point, the boost converter will not be able to maintain a regulated output voltage, hence it will stop charging.

What if you really want to dump the juice from old AA batteries to your phone? There is actually a solution, and you should keep reading below.

Step 6. LiPo Charging

In addition to USB charging, one of the new features of the AASaver 2.0 is LiPo charging. If you have a 3.7V LiPo battery (we carry an inexpensive 700mAH LiPo battery at Rayshobby Shop), you can plug it in to the LiPo Out jack. This allows you to charge the LiPo battery from AA batteries with an adjustable charging current (from 10mA to 200mA). Once the battery is charging, you should see the green Charge Indicator LED light up.

To change the charging current, use a small screw driver to gently rotate the trimmer (SMT POT). The trimmer is very fragile, so be careful when adjusting it. The flat side of the trimmer top is the tail, and the opposite side is the head. The charging current is indicated by where the head is pointing to.

How does the adjustable charging current help? As I described above, the issue with old batteries is that they cannot provide much output current. But they should still work if you ‘dump’ the power slowly. For example, they probably can’t provide 100mA output current at 5V, but they are probably good with 20mA current at 5V. So the trick is to dump the power slowly into a LiPo battery. This is analogous to having a water pipe with very limited capacity: you can’t draw water from it at a high speed, but you can let it drip slowly into a bucket (in this case the ‘bucket’ is the LiPo battery). Then later you can dump the water from the bucket at a much faster rate.

So all in all, if you have an old pair of AA batteries, you can’t charge USB devices directly. But you can still use them to charge a LiPo battery at a slow rate. To do so, adjust the trimmer so that the green indicator LED will remain on. If the LED goes off, it mean either the charge current is too high, or too low. So adjust the trimmer to keep it on. As you will see in the next step, with the LiPo battery, you can then charge USB devices with much ease.

Step 7. Using LiPo Battery as Power Source

To use a LiPo battery as the power source, simply plug it in to the LiPo In battery jack, then make sure that you turn the Source Selector Switch up to point to LiPo In. This selects the LiPo battery as the power source, and everything else works the same way as before.

All right, this is the end of the story. I know this post is very long, but most of it will be moved to the AASaver Homepage after I refine the text and hear back comments and suggestions from users. If you are interested, please place an order for the AASaver from the Rayshobby Shop. We have a limited amount right now and more stock will become available in the upcoming weeks.

Questions and comments? Post them below or on the Rayshobby Forum.

Posted in LED Projects, Product News | Comments Off

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