trigger

Hi all, Check this out....... may be useful for this topics http://www.edacafe.com/books/ASIC/Book/CH03/CH03.2.php (or the whole free ebook at http://www.edacafe.com/books/ASIC/ASICs.php)

can we say virtual ground = opamp dc offset voltage?

How are about the shipment to people in hong kong like me?

AM demodulation is envelope detecter only. And the loudness is depends on the modulation depth of the source. And IF is the resultant frequency of the difference between the local oscillator and the carrier frequncy, which is to lower the frequency for demodulation.

there are thousands of factories in china..... some of them are qualified manufacturers of those large brand names, where they will have a better qualifty control + ISO certificate. some don't have anythings.... mostly these only supply to china local stores..... somhow these un-qualified products may leak out to other countries....... thus.... I prefer a brand name one in a proper local stores

I will not buy cheapo light bulb without a good brand name...... So I prefer to pay double more to get somethings under the name of philips

first, you got to know it is a common anode or common cathod 7 segment LED display. second, the fastest way to check the a, b, c...g is to directly check which pin will lit its corresponding segment by applying power across the pin and the common terminal. Remember, test is always the fastest way rather than asking, especially there are many specification on 7 segments LEDs.

Here is some examples in interfacing RS232 and parallel port on PC: http://www.beyondlogic.org/

use a coil and opamp circuit, you can convert AC current to DC voltages.

audioguru, Your project is great, save me from thinking on how to flash a bunch of LEDs with 2 AA cells... I will build my own too, not for $$$, but for a special gift to my girlfriend..... ;D The IC with prefix CD40xx may not work at 3V but the 74HC40xx should be work fine with 3V..... I gotta check this out. Anyway thanks!! ;D

try to find switches info from the following website http://www.wealthmetal.com/products.html 8)

No offend here but I want to tell some facts. Shenzhen, a city in South China near Hong Kong, got very cheap components since many factories around. And there is a shopping mall that have many many shops to sell components in very low price. Imagine just needed USD$2.5, you can get 1K pieces of SMT resistors (a tape). If I start business in Hong Kong and have sent components to US or around the world, I am rich ...... :P

Good! IR is also a good solution. For RF, it will take more time for you to troubleshoot and needed more equipment..... But should be take great care if your circuit is used under bright light . Since the ambient light contain full spectrum of frequencies which may jam your IR signal or shorten the link distance.

not just east copy west.... but also some US fabless will copy and improve the chips. One example is california microdevice (hmm... hope I haven't mistaken) .... they have single opamp with low noise and wide bandwidth which is pin to pin compatible with NS one..... but I forget the part number...... And that single opamp is used in an AGC video circuit with very fine performance....... even better the original one......

Suraj, Woo...... I am a bit of awaken with your knock on my head :P ;D I am now studying those information now.... And I want to work this out as I think it will be a nice tools for development...... Trigger

audioguru, May be you are National semiconductor supporter, but I am not. Mostly used in products will no longer be NS brand, but some others. Check the link here: http://databook.kec.co.kr/Products/item_list.php3?type=X&key1=E&key2=100 Check what the specification on KIA358 and KIA324..... compared with what you found in NS. You will noticed what actually I mean previously. These ICs are pin to pin compatible with better specification. And of course I know LM324 is quad version of LM358, don't just treat me as a fresh graduate..... :P

I can tell, LM324 used as audio amp is much worst than using LM358. As circuit designer, we always like to use the perfect components.. however, the reality will not let you to, esp. your boss is barking loud to stop you. And I can tell, some of those opamp, are now produced by Korean or taiwan (some even china); some of them, also being modified by US fabless company with better specification. So in some case, the chip is always improving rather than continuous with their noisy specificaiton.

pre-scaler?

some of the opamp are crap but that doesn't mean it is not suitable for products. I can tell, LM358 is still widely used in many everyday products..... why, because it is low cost....... (the price of IC is not what you seen in the local store) Actully, no manufacturers will care about the noise and distortion but price.....

I think the quoted price of those chips are in HK dollor, right? If yes, very good price..... Oli, can you tell me where you get them? Local stores? Thanks.

thanks Suraj, But those programmers are using parallel port instead of serial port. I also come to some parallel-to-I2C circuits, with complete source code. May be I have to use an MCU to translate the serial data to I2C/SPI. Anyway, thanks for advice. I will post something out once I got some progress. ;D

Hey Oilhou, I am same as you, come from Hong Kong. ;D There are some places where you can buy components, like in Sham Shui Po Ap liu Street, IC master in ShanPoKwong, Leader in Kwun Tong, etc. If you can't get required components, you can try local RS or Fernell, there you should get some..... but expensive. Or you can go to Shenzhen for components..... but less reliable... Hope this can help.

I saw also in a mosquito bat....... a cheap tools to kill mosquito with sparks......... Inside have transformer, should be step up the DC voltage.... But I won't copy its circuit..... as the soldering is so horrible....... and I threw it away once I discovered that........ :P

Ante, I have come to such problem yesterday.... and found the loading on the pages were quite slow....... and then turn out the error pages as shown. But try reloading pages seem to cure the problem. Today there is no more such problem and all are working fine, included the "new" button.... so you better check with Mixos.... Trigger.

I have such problem yesterday. I think most likely the database server too busy in processing our browzing.... anyway..... it is fine now......