Twitter Quiz – the answer

NEWPIC

Filtering capacitors routing is very important in digital world. One and same circuit may work or may not work correctly if routed bad or good, although schematic is same and components are same.

In this quiz the correct answer is Right circuit is better routed as it has twice less wire lengths and thus twice better prone for injected noise and emitted noise through the power supply wires.

Explanation is simple:  All digital circuits have power supply spikes when change their state from on to off, inside one microcontroller there are thousands of such digital switches which produce high frequency noise on the power rail lines. They may be simple represented by resistors from Vcc to GND which value changes very quickly and change the power consumption for very small amount of time (nano seconds). For these high frequencies the PCB tracks are not just conductors but behave also as inductors, although with small inductance when frequency is high they start to play significant role and do not allow the power from the power supply to feed the digital circuit immediately, and if you look with scope you can see lot of noise up and down spikes caused by the changed power consumption and track inductance, to clear these spikes capacitor is placed close to the digital IC which is acting as reservoir with energy and feed energy for these short times until the main power supply energy overcome the inductive resistance and come to the digital circuit. In our case left side circuit have two times longer tracks which go to the capacitor and will emit and receive twice more noise than the circuit in the right hand side.

Right side circuit have one disadvantage though – it allow more cross talk between the two VCC power supplies, i.e. Vcc1 will inject more noise to Vcc2 and vice versa, so of course best solution is to place two capacitors, so it’s up to engineer decission which in his case is better to spare one capacitor and allow more noise cross-talk between Vcc1 and Vcc2 or to place two capacitors and rise the BOM 🙂

All above is based on the assumption for high frequency digital design as the filtering capacitor is with small value 100 nF, if this was audio circuit with low frequency power noise the left circuit is better, it’s also known as star topology, I guess this confused most of the responses, for low frequency and if the filtering capacitor was with big value 1000uF the left side circuit would behave better as in this case PCB tracks do not behave as inductors, but the cross talk between the different Vcc will be minimal.

Random.org says our winner is @avrnoob, please contact us for your present – OLinuXino (paper) notebook:

notebook

see you next Friday 🙂

Twitter Quiz – PCB routing

PCB

Many IC have more than one VCC . All we know why filtering capacitors are add to VCC power supply, but if we want to spare capacitor and use one capacitor for two VCC signals on the VCC how is the correct way to route it like on the left hand side of the picture or like on the right hand side?

Please answer on Twitter you have time until Monday 🙂

Twitter Quiz – Restart

quiz_00005

Do you miss our Friday Twitter Quiz?

We certainly do 🙂 and will going to re-start it again.

So be ready for today 17.00 oclock we will post our Quizz question on Twitter and will wait you to reply till Monday! Then Random.org will pick one of you for the prize.

Friday Free Board Quiz – Week #76 prize is ARM-JTAG-CooCox

Image

ARM-JTAG-COOCOX is an ARM debugger based on CoLinkEX design. It is meant to work out-of-the-box with the free CooCox IDE. It can also be used with Keil MDK and IAR EW IDEs (the driver for IAR is still not perfect) via external plug-ins.

You have chance to win the prize if you participate our Quiz.

To participate in the Quiz is enough to Re-tweet the Quiz announcement message.

To double your chances you have to answer the Quiz question :)

Today at 17.00 o’clock our local Bulgarian time (GMT+2) we will post on Twitter our questions.

You have one hour to reply to our tweet with the correct answer.

At 18.00 o’clock we will count the correct answers and ask random.org to generate random number in range then announce the winner and ship the board by airmail on Monday.

Friday Free Board Quiz – Week #75 prize is BB-A4983 motor driver

Image

BB-A4983 is stepper motor driver for 2A up to 35V motors.

You have chance to win the prize if you participate our Quiz.

To participate in the Quiz is enough to Re-tweet the Quiz announcement message.

To double your chances you have to answer the Quiz question :)

Today at 17.00 o’clock our local Bulgarian time (GMT+2) we will post on Twitter our questions.

You have one hour to reply to our tweet with the correct answer.

At 18.00 o’clock we will count the correct answers and ask random.org to generate random number in range then announce the winner and ship the board by airmail on Monday.

Friday Free Board Quiz – Week #73 is Arduino with Tiny85 FOSDEM-85 edition

Image

FOSDEM-85 is DIY Arduino KIT with ATTiny85 specially made for FOSDEM Hackathon.

You have chance to win the prize if you participate our Quiz.

To participate in the Quiz is enough to Re-tweet the Quiz announcement message.

To double your chances you have to answer the Quiz question :)

Today at 17.00 o’clock our local Bulgarian time (GMT+2) we will post on Twitter our questions.

You have one hour to reply to our tweet with the correct answer.

At 18.00 o’clock we will count the correct answers and ask random.org to generate random number in range then announce the winner and ship the board by airmail on Monday.

Friday Friee Board Quiz – Week #70 prize is SHIELD-LCD16x2

Image

SHIELD-LCD16x2 is Arduino compatible serial LCD 16×2 characters with backlight and 4 buttons which are controllable through UART or I2C.

You have chance to win the prize if you participate our Quiz.

To participate in the Quiz is enough to Re-tweet the Quiz announcement message.

To double your chances you have to answer the Quiz question :)

Today at 17.00 o’clock our local Bulgarian time (GMT+2) we will post on Twitter our questions.

You have one hour to reply to our tweet with the correct answer.

At 18.00 o’clock we will count the correct answers and ask random.org to generate random number in range then announce the winner and ship the board by airmail on Monday.

Previous Older Entries