Recent content by edmondng

get a good grasp of what antenna is, the types out there, the differences between them. it will help you understand why people build antenna and use different antennas in different application as well as drawbacks. once you understand this, it will make more sense to build one.

radioschack. they have some kronus tool sets for like $15/$20

How do you find voltage drop produce by the coil/inductor? I know V = L(DeltaI/DeltaT), so if i have 1A flowing and 2mH at 100kHz, does that mean i can generate drop upto 200Vp-p?

there are 3 types of rfid, passive, semi-active and active. Passive rfid harvest the energy from the coil so it only works when it is close to detect the energy (inches). You will need active rfid. Try digikey. there's a reader from atmel u2270B, add that with a controller and a tag to read.

yes, thanks for correcting me

capacitance has inductance as well. its generally Ceff = C + L//C or some other combination. As frequency increases, impedance drops, and once it gets beyond a point where inductance is dominant over capacitance, impedance goes up.

ok, so mainly the difference is voltage level, and as long you meet the requirements to toggle the gate it should work. One more thing, aren't all chips these days made CMOS, because its lower power consumption than TTL? How do i know if a chip is TTL or when to use 'T' type package?

Berkeman, what is the main difference between ttl compatible and cmos compatible? A 'non t' part has the conventional cmos input threshold, while ones with 't' has both cmos and ttl compatibility. Does that mean if i use a 't' part it won't drive a 'non t' part? I thought as long as it meets the...

http://en.wikipedia.org/wiki/Transformer

its based on the ratio as stated

capacitance in parallel is same as resistor in series and vice versa. c = permittivity*dielectric*area/distance If you have a sphere, it will be an integration of series of capacitance depending on the diameter of the sphere at different location. At the tip of the sphere, the dielectric...

the electrician already explained. its called natural log. In your calculator natural log. Its not 'In', the symbol is Ln, or some people write L as 'l', and unfortunately 'l' looks like 'I' http://en.wikipedia.org/wiki/Natural_logarithm

i was going to suggest DDS but doubt there's any chip out there to work with

delete It would be best if you draw a simple circuit, with voltage and 1 resistor. What is the current? What happens if you add 2 resistor in series now. What is the current and voltage between both resistor. Keep adding, another resistor in parallel with 2 resistor in series and find...

you can make current go any way you want as long as you stick to the same convention throughout the circuit (this is just something to keep in mind) In this case, you have 3 lines in your circuit with respect to that node. Current is not pointing up. That is just a symbol for current. It says...