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I am thinking of a circuit where I can give out I2C/SPI commands/data to some ICs (like 24Cxx, some RF PLL, ADC, etc) through RS232 port on my PC. That will enable me to try some command codes or build test jigs. Anyone get ideas?

May be this site, will give you some ideas in the experiment..... http://www.geocities.com/vsurducan/electro/micro/micro.htm

I think it is a network resistor more than an IC.... ::)

Is the microwave frequency equal to the resonant frequency of water?? When the microwave applied, the water molecule will vibrate more fiercely?? and finally generate heat?? anyone can confirm this??

check the following link for its datasheet http://www.secomtel.com/UpFilesPDF/PDF/Agilent/PDF_DOCS/SKYDIODE/03_SKYDI/HSMS2850.PDF It is from Agilent (previously HP). But I can't help with the dealer ....... sorry

I think you can do some time delay circuit on the reset pin of IC 4013. Just simple RC can do. I have tried a few circuit on 4017 with about the same problem of random and I can eliminate them with such addon. So good luck then. ;D

audioguru, Noope I am not going to build this circuit. Just quote a pass experience in handling condensed microphone circuit in manufacturing products (say for example, an microphone preamp stage inside an analog cmos camera connected to your VCR/TV). The suggestion is to minimize the noise/ripples come from the path of the supply, which is generated by other parts of the circuit. You may noticed "humming" sound at the later amplify stage if that modification hasn't included. Remember, you got to eliminate the possible noise before tha amplify stage else no matter what opamp you are using, you are going to amplify both the required signal and noise..... and gradually make the circuit fails.

For me, I will divide R1 into two 5K ohm resistor in series and with a 22uF capacitor connected between these two resistors joint to gorund. That will reduce much noise from the power source to the microphone.

OK, I finally find 3 books for Signal Integrity... in pdf format http://downloads.pcbtech.cn/SI-Book.rar (35MB) These books may be violating the copyrights.... so download them at your own risk.

Are there any good books or websites which have deep down discussions in Signal integrity on PCB layout (high speed digital circuit) ?? Thanks alot.

batteries always start at 1.5V (some I have measured up to 1.7V)and then gradually down to 1.2V... and then dead.. so if you really want to power the circuit with exact 9V... AA or AAA are not fitted your application. try to use the 9V cells.... or more AA/AAA cells... For 100mA current.... it really depends on the power rating (check the datasheet or the graph on it) on the batteries.... say for example, alkaline AA cell is approx. 1000mAH (i.e. provide 1000mA an hour), divide this parameter with the current drawn and you will get your system will survive for 10hours.. This calculation isn't the exact figure as the cells are usually not the same figure and this calculation assumed the circuit is constantly drawing 100mA... but it just give the goood estimation.

well..... I can read those words in www.163.com .... cos I am from Hong Kong... 163.com is just a search engine in china.... and provide free email address.... so the name TCL that guy mentioned is a china brand home appliances manufacturer......

I think this kind of capacitor is just used for PCB with vias plated.... else you can't have the contact....

is the line-in muted?

google is really a good search engine....... uPA2003 http://www.necel.com/nesdis/image/IC-1401.pdf

how about a magnetic switch, some step counter use it. Also most now use plastic arm to do so. I will try to search my old stuff to see if I can get you a picture of these mechanism.

The higher the power dissipated by the regulator, more the ripples at the output. It is what I learn from real product design. So my experience is the input voltage usually 20% more than the specification required in order to give that 20% safety margin. It will not cause much heat generated.

The structure of Long wave radio receiver should be more or less the same as that of AM radio. Just the difference in frequency and the corresponding coils.

There are many types of sensors but I have no idea what you want. Please give more details.

nice link...... thanks!

hmm...... that circuit may affected by ambient light source.... using a frequency source to lite the IR LED may do a better peformance.

It sounds like a maze mouse project..... ;D

I think I am wrong...... because those ICs I mentioned isn't operate in 1.5V...... And I think it is quite difficult to source for radio IC which operates in 1.5V for howbrew...... I am playing now with Toshiba TA2104 but its minimum voltage is 1.8V........ :-[ And MC3361 and MC3362 are not amp, they are IF front end where they are widely use for wireless intercom circuit for many years...

Good to hear you have good progress ;D And for FM receiver, you can try to use simple FM radio receiver ICs. They are served you well (for which your FM transmitter is within the broadcast band 88~108MHz) ICs like TDA7000, TDA7088, MC3361, MC3362 may fit your needs.. Hope this help.

Try to add a resister (say 10ohm carbon film; 1/4W should be ok except you need to drive high current components)/choke coil (10uH I think is ok) between the supply and the unit, plus a ceramic capacitor to ground. This may help a little bit if the ripple of the supply is high.