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Testing the TPS61092 Boost Converter

For my current project I searched for a good boost power converter which is able to deliver continuous 400mA power for various sensors.

There are an endless number of good boost converters around, but not many can be hand soldered to a board. I would really like to see some like the TPS61092 with SOIC or similar packages. The biggest problem seems to be the heat transport, why most chips have to be mounted flat on the board.

Before using the chip in my project, I created a small test board. Using this board I can test various things. First I liked to test the performance under load. Next I tested if the chip can be hand soldered and finally I tested the final board layout I will use in my project.

Performance

The performance of this chip is really good, producing a very stable output. I designed everything for a load up to 2A with all suggested components from the specification. There will never be a higher load than 0.5A, so I probably could use a smaller coil for the final project.

thermal image

Running under 0.5A load from 3.3V for over half an hour, the chip stays quite cold. Even in my case, where the chip bottom is not directly soldered to the board, it seems to be able to transfer the heat into the board. This is nicely visible in the thermal image of the board.

The Board

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The board was produced by OSH Park in a good quality. If you like to experiment with this chip, you can order this board very cheap at OSH Park using the following link.

Continue Reading

Boards in Good Quality from SeeedStudio Fusion

SeedStudio offered me a coupon to evaluate their PCB service “Fusion“. I am currently working on a new project, so I gave this service a try. I used the following options ordering the two boards:

PCB Dimensions 68mm*108mm
Impedance Control No
Surface Finish HASL Lead Free
Minimum Solder Mask Dam 0.4mm↑
Copper Weight 1oz.
Plated Half-holes / Castellated Holes No
Minimum Drill Hole Size 0.3mm
PCB Color Blue
Base Material FR-4 TG130
No. of Layers 2 layers
PCB Quantity 5
Blind or Buried Vias No
PCB Thickness 1.6
Trace Width / Spacing 6/6 mil

I payed $27.40 for five boards with the option shown above and there were additional $20 shipping costs.

My board design has a very low quality class B4: Minimum drill size is 0.35mm, minimum trace size and spacing is 0.2mm.

Ordering and Shipping

The order process was very simple. The website provides an assistant with all possible options and calculates a quote in real time. I just noticed these minor things:

  • The shipping cost is not displayed in this quote.
  • The dimensions were not correctly extracted from my Gerber files.

The production of the boards and the shipping was quite fast, the whole process only took 10 days until the packet with the boards arrived.

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The boards were well protected in the package, so there were no scratches from the shipping of the boards.

Quality

The boards have a good quality for the chosen options and the price. The alignment of the layers is not perfect, but everything is in an acceptable range.

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The front side of the two boards. Continue Reading

Plant Watering Sensor Foot Parts from Eurocircuits

I received the foot parts of the plant watering sensor from Eurocircuits. As you can see, they have the same great quality as the head parts. Eurocircuits removes any bridges from the boards in a very clean way, so you get the boards with exactly the shape you designed. This saves a lot of work […]

Eurocircuits Delivered Astonishing Perfect Panels

I ordered a single panel as a test for the production version of the plant watering sensor and I got astonishing perfect panels from Eurocircuits. Even I only ordered just one, I got three perfect panels in gold. Thank you very much Eurocircuits! As you can see from the photos, the quality of the panels […]

How to Design a Cheap Plant Watering Sensor (Part 5)

This is the fifth part of the meta-tutorial, where I talk about designing a cheap plant watering sensor. If you did not already read the firstsecondthird and fourth part, please do it now. These parts contain a lot information which lead to this point of the tutorial.

The fourth part ended with step 20, where I did usability tests and stability tests using the preliminary firmware. This article will focus on designing the final board for the project.

Step 21: Design the Final Board

Designing a good board is like one of these puzzles with quadratic tiles, where you try to lay down a 3✕3 set where all edges match. Often a small change result in many follow up changes, so you have to rip-up a lot of routes and design them in a new way.

My goals for the board were:

  • Everything, except the two LEDs, should go to the top side of the board.
  • Reduce the amount of vias to the absolute minimum.
  • Create a ground pour, especially around the oscillator part, to reduce noise.
  • Move the button as far as possible from the oscillator to minimise the influence if the user presses the button.
  • Make it as small as possible.

I worked with small iterations, checking the design after each iteration and checked the design against my goals. To keep track of the changes, I versioned each larger iteration. This way I could go back at a later stage for comparison or if a change did not turn out well.

The Tools

I worked with Autodesk Eagle to create the board. This tool is in the current state far from perfect, but it is cheap and has all required features for the task. For me personally, these are the features I need to design a board:

  • Smart routing editor which is linked to the schema.
  • Quick and easy way to create vias and see the required connections.
  • Good library support for symbols and packages.
  • Design rule checks.
  • Quick board preview to check label placement and design.

I described some issues of Eagle in this post:

12 Time Wasting Issues in Autodesk EAGLE

As you can see, these are not very advanced features and are supported by almost all good board editors. I never use the auto router, because I do not have time pressure or have to do repetitive tasks. Continue Reading

A Versatile ATtiny Programming Adapter

As mentioned in my article about designing a cheap plant watering sensor, I built a small adapter which can be used to pre-program the ATtiny13A. This is necessary, because once soldered on the board, I only have a debugWire interface, which has to be enabled first.

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The adapter has a small 50mil JTAG header, where the Atmel ICE can be connected with the board. There is also room for a USB mini jack, which is used to power the MCU while programming. A small on-off switch is used to power the MCU and a LED is placed as indicator to see if the MCU has power. The assembled board looks like this:

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One of the DIL/ZIF adapters is mounted on top of the female headers. Most of the adapters for SO-8, SO-14 and SO-16 will work with this board. Continue Reading