Flexible printed circuits are useful when the size and shape of your invention is integral to its overall design. Very many consumer electronics gadgets have them inside: in mobile phones, cameras, etc. Tips for Building a Flex Circuit article tells that because of the unique characteristics that set them apart, an electronics engineer must consider additional factors when designing these circuits: the degree of bending, the tightness of the bend, how the bend will be formed, and how frequently the circuit bends. Tips for Building a Flex Circuit article tells the key factors to consider when building a flex circuit board.
Basics of Flex Circuit Design article tells that reliability, designers must create flex circuits that are neither too thick nor bend too much. The neutral-bend axis is a key concept in flexible-circuit design: tension or compression on the outer layers of the circuit depend on their distance from this neutral-bend axis and the radius of the bend. A circuit should flex no more than necessary to handle the goals of the design. In general, 90° is considered the maximum angle any circuit should bend. Avoid unnecessary thickness. Tight bends conductor traces boost the risk of circuit damage. Small conductors of less than 10 mils can tolerate compression better than stretching. If you use surface-mount (SMT) components, be aware of their special requirements. Avoid “discontinuities” in the bend area. Copper plating is less ductile than rolled, annealed copper, making it more susceptible to cracking when flexed.
Hackaday.com lists many flex circuit projects that could be worth to check out or DIY hardware hackers. They prove that flex circuits can be successfully build even on home laboratories.
Hackaday article Hand placing flash die to make USB drives tells how boards inside USB drives populated. The article points to Where USB Memory Sticks are Born article that tells that once the bare die FLASH chips are screened for functionality, they are placed by hand onto a PCB (using some sort of tool made out of hand-cut bamboo). According to the article this is not an unusual practice for a value-oriented wirebonding facility.
The markings on SMD components have been always hard to read. Besides the fact that the numbers and letters in them are very small, the number coding used on them is different than what is used on traditional though-hole components (the reason is that there would not be enough space to print any long codes to those components). How to decipher those SMD resistor codes has been always a hard task. Pages like SMD Resistor Coding, The SMD Codebook, Marking SMD have tried to give some help on this.
10 Ways to Destroy an Arduino article tells how you can accidentally destroy Arduino board. Use a sledgehammer, fire a bullet at it, throw it into a pool….that’s not what we’re talking about. We’re going to show you how to electrically destroy your Arduino:
Method #1: Shorting I/O Pins to Ground
Method #2: Shorting I/O Pins to Each Other
Method #3: Apply Overvoltage to I/O Pins
Method #4: Apply External Vin Power Backwards
Method #5: Apply >5V to the 5V Connector Pin
Method #6: Apply >3.3V to the 3.3V Connector Pin
Method #7: Short Vin to GND
Method #8: Apply 5V External Power with Vin Load
Method #9: Apply >13V to Reset Pin
Method #10: Exceed Total Microcontroller Current
When there are problems or potential problems, there are often commercial solutions to them. 10 Ways to Destroy an Arduino article was written by makers of The Ruggeduino board. Besides telling the problems, the article gives ideas how to solve most of those problems (interesting reading).
The Ruggeduino is a ruggedized Arduino-compatible microcontroller board. It’s features include overcurrent and overvoltage protection on all I/O pins and 5V/3.3V outputs, ESD protection on all I/O pins and USB port, total microcontroller overcurrent protection, and operation at up to 24V. I have written earlier on my blog on that board at http://www.epanorama.net/blog/2011/08/23/ruggeduino/.
The video was pretty well made and I can fully agree most of the things said on the video. Here are some information picked from the video.
Here we discuss the circumstances of when it is appropriate to use a twisted pair RCA cable vs a Coaxial RCA cable:
“Coaxial RCA cable is good and twisted pair is better”
“That’s not the case”
“There are specific cases where you would want to use each one of them”
You want to use coaxial if you have amplifier with single-ended inputs. In those inputs the outside of RCA is grounded. This type of inputs are used on average amplifiers (70-80% inputs in audio equipment). So for normal single ended RCA connections the coaxial cable is the right cable type.
The video says that if you have amplifier with differential input you want to use twisted pair wiring. Those are found on some of the high end amplifiers Only a small percentage of equipment have this type of RCA inputs.
If you mix those different cables and different input types, they don’t work that well: the connection become easily noisy.
According to the video if you have amplifier with differential input you would want to use twisted pair wiring. Those are found on some of the high end amplifiers Only a small percentage of equipment have this type of RCA inputs. I cam agree this. I have very rarely seen those differential input RCA connectors anywhere except some car audio equipment.
If the head unit has SE outputs and the amplifier has SE inputs = coax cable
If the head unit has SE outputs and the amplifier has Diff inputs = twisted pair
If the head unit has Diff outputs and the amplifier has Diff inputs = twister pair
If the head unit has Diff outputs and the amplifier has SE inputs = bad no matter what as you will shorting out half of the head unit’s outputs. In this case you would need an amplifier with Diff inputs or a converter to convert the head unit’s outputs to SE
According to those comments you need to what type of inputs and outputs your devices have to select the most suitable cable type. The differential inputs and and outs are like how XLR /balanced inputs work.
I said in my original Unshielded RCA cable is bad design article: When you wire unshielded twisted pair to unbalanced signal source and receiver RCA connectors, most of the good properties of the UTP cable noise rejection are lost. This holds true.
When you have system where you have unbalanced signal source and differential receiver, you get some of the benefits of differential system, but not all. The differential RCA receiver can get rid of the noise that is coupled as common mode noise to the twisted pair. In systems that use Balanced Line Technology the twisted pair cable construction combined with differential receivers and signal sources make sure that both inductively and capacitively coupled external noise to the wire pair gets converted to common mode noise that can be removed in differential receiver.
When you have system where your signal source is single-ended, things are somewhat different. Let’s consider first case where the single-ended signal source is grounded. In this case one of the signal wires is at ground potential and other carries the signal. The coupled magnetic fields generate the same amount of noise to both wires, so the magnetically coupled noise is still removed well differential receiver.
So I don’t think that unshielded twisted pair cable in this case would guarantee to be considerably better that coaxial cable. Depending on your noise source type, it could be somewhat better (only magnetic noise) or it could be considerably worse (against capacitively coupled noise on high impedance systems).
The situation for capacitively coupled noise is somewhat different if the signal source equipment is not grounded. In this case the impedance different the capacitively coupled signal sees is much smaller, so the signal gets coupled more equally to both twisted pair wires (not completely equally), and the differential receiver can get rid of most of the capacitively coupled noise to the cable. The downside with ungrounded mains powered equipment is that there is always some leakage from mains to equipment case, and this leakage can easily generate common mode noise to the cable that is much higher in amplitude than the audio signal on it (few volts to tens of volts depending on impedances and leakages). Usually at least some of that voltage gets to audio signal as noise because the differential inputs have their limitations on their common mode noise canceling capabilities (limited CMRR capabilies typically 40-70dB and sometimes the noise voltage can exceed the common mode voltage range the input can operate with). So if you are working with differential inputs you generally want the signal source to be grounded in way or another (or to be completely floating battery powered gadget or microphone).
The best cable for a setup that uses differential RCA inputs and single-ended output would be shielded twisted pair. The twisted pair construction would perform well against magnetic noise, and the shield (grounded at least on signal end) would get rid of the capacitive noise. So this would be the optimal cable.
A differential input only really works best with a balanced output and twisted pair/screened interconnect cable. This is how professional audio equipment that use Balanced Line Technology and XLR/phone connectors are typically wired. With this kind of balanced output and differential input system an unshielded twisted pair can also work acceptably.
The second best option for interconnection is unbalanced (single-ended) output wired to shielded twisted pair cable that is connected to differential input. Trying to use unshielded twisted pair here will give considerably worse performance.
So I can still stay on my original claim that Unshielded RCA cable is bad design. This will hold true very well. Exceptions to this rule (if there are any) are really rare. I can also say that twisted pair construction on RCA cables is better on some applications when the cable construction is shielded twisted pair.
In case the twisted pair cable used for interconnection is shielded twisted pair cable, I can agree on those comments on Truth about RCA signal cables video page:
If the head unit has SE outputs and the amplifier has SE inputs = coax cable
If the head unit has SE outputs and the amplifier has Diff inputs = twisted pair
If the head unit has Diff outputs and the amplifier has Diff inputs = twister pair
If the head unit has Diff outputs and the amplifier has SE inputs = bad no matter what as you will shorting out half of the head unit’s outputs. In this case you would need an amplifier with Diff inputs or a converter to convert the head unit’s outputs to SE
Feel free to comment if you disagree with my analysis and conclusions.
HackEDA takes all those basic building blocks and promises to create a custom Eagle schematic with all the parts your project needs. This looks like a good idea to develop more. Think of it as a mashup tool for electronics: the next time inspiration strikes, there’s that much less between you and the hardware you need to make it a reality.
In my posting War on DIY Electronics I already told that that the trend is that electronics is heading to be less and less hackable. Wired has an opinion article Forget the Cellphone Fight — We Should Be Allowed to Unlock Everything We Own that has many good points that I can agree on. USA Congress is working on legislation to re-legalize cellphone unlocking. The copyright laws that made unlocking illegal in the first place and it makes many other things you might like to do illegal in USA.
Who owns our stuff? The answer used to be obvious. Now, with electronics integrated into just about everything we buy, the answer has changed, because in digital age even the physical goods we buy are complex (usually run by complex software that runs on embedded computer or many of them). Copyright is impacting more people than ever before because the line between hardware and software, physical and digital has blurred. We really don’t own our stuff fully anymore – the manufacturers do own at least some some important parts of it.
Because modifying and repairing modern objects (home electronics, cars, etc..) requires access to information (manuals, error codes, and diagnostic tools) that manufacturers don’t like to give out. Property rights issue is turning many regular people into criminals: When they try to do something manufacturer don’t like, the manufacturers claim those people are illegally “reproducing copyrighted material.” Fixing our cars, tractors, and cellphones should have nothing to do with copyright. We should be allowed to unlock everything we own.
What did the iPhone look like before it looked like an iPhone? Apple’s popular product looked radically different in the early stages of development (like many other high tech gadgets). Image of the Day: iPhone prototype from 2005 article gives you view of the early iPhone prototypes. Check out the article for interesting photos.
It is quite common to have this kind of ports in development prototypes, because ports like Ethernet and serial simply to make working on the device easier.
Why does not my tablet touch screen work when powered with third party mains power supply, but works with the original power supply? This happened to me. The power supplied I had were both for tablets (different tablets) and had similar basic characteristics (same current and voltage ratings).
The reason why the other power supply caused the touch screen to fail was related to the noise given out by the power supplies and the touch screen electronics sensitivity to this noise. One power supply outputs more noise than the other. How this noise affect the touch screen electronics is shown in this picture MoU regarding Harmonisation of a Charging Capability for Mobile Phones, June 5th, 2009.
This is nothing new, just now well documented what happens. This same happens with practically any today’s mobile phone charged based on switch mode power supply technology. Smart-phones and tablets need to be designed so that they can live with it. And power supplies needs to be designed to that they do not put out too much noise. Some details on this can be found at my EU standards for common mobile phone charger article.
Dealing with noise is an important aspect of any real-world electronic system, especially in a capacitive touchscreen in a cell phone or tablet. Noise Immunity of Touchscreen Devices web page tells that while there are many sources of noise that can interfere with capacitive touch sensing, the most prominent ones originate in displays and battery chargers. Cypress Offers Battery Charger Noise Immunity web page tells that low-cost chargers lack critical noise suppression components and can generate tens of volts (peak to peak) across the frequency spectrum of 1 Hz to 1 MHz. These voltage spikes can go directly into the touch panel during the presence of touch, severely impacting touch performance. Mobile phone vendors have worked together to create EN 62684 and EN301489, standards that regulate the noise spectrum for battery chargers.
Cypress Offers Battery Charger Noise Immunity web page tells touch screen controllers are developing all the time. It tells that a new TrueTouch feature Charger Armor enables touchscreens in mobile devices to function seamlessly by preventing inaccurate touch readings, which are often caused by common-mode noise from inexpensive chargers.
It is a good thing that those touch controllers are improving, because many people (electronics designers and users) struggle to overcome charger noise.
