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  1. KrisBlueNZ

    Transmit and receive parallel data through radio link

    OK cool. Something based on a 74HC165 and a 74HC595 transmitting a start bit, some data bits, then an idle gap, would probably be pretty good. I'll draw something up in the next few days, OK?
  2. KrisBlueNZ

    Transmit and receive parallel data through radio link

    And the transmitter just takes a digital data stream in, and that stream is reproduced at the receiver? Do you know the maximum data rate? It's not important; I'm just interested. Also is there any kind of clocking at either the transmitter or the receiver? And you want to broadcast...
  3. KrisBlueNZ

    Digital Circuit Help (Custom Logic Gates)

    Hi there and welcome to Electronics Point :) That assignment does have an answer. I guess you're not looking at it the right way. Start by studying the truth table of that gate they've given you. What can you make it do? What happens if you connect the inputs together? That would be the first...
  4. KrisBlueNZ

    short circuit protection for power supply

    No, don't Google crowbar circuits. A crowbar detects overvoltage at the output of a regulator, not overcurrent. You really want a circuit in series with the input to the regulator that monitors the current using a shunt resistor and latches into a state where it activates the buzzer and removes...
  5. KrisBlueNZ

    Measuring Sine Wave Using ADC

    According to Nyquist, half of the sample rate, i.e. 66.5 kHz. But in practice, up to about 10 kHz if you want to be able to see the rough shape of the waveform.
  6. KrisBlueNZ

    Basic 555 timer

    OK, that relay is a Multicomp HRS4-S-DC12V with a coil power of 720 mW which corresponds to a current of 60 mA. Its coil is connected between the positive rail and the 555's output, with a diode (D2) across it. The LED (with its series resistor) is also connected across the relay coil. This is...
  7. KrisBlueNZ

    Transmit and receive parallel data through radio link

    What kind of transmitter and receiver are you using? There are various ways of approaching that requirement. One is to use a "dumb UART" at each end. such as the ancient Harris/Intersil 6402. But I just checked availability for these, and Digikey doesn't have them and they're USD 30 each from...
  8. KrisBlueNZ

    Assembly statements

    Likewise. In my previous job, we used several small micros, including AVRs. Back when PICs started getting popular, we looked into them, but we unanimously rejected them because of their poorly designed architecture. Just too many workarounds and kludges. Yeah, tell me about it. I've been...
  9. KrisBlueNZ

    Need help with relay calculation

    You shouldn't be surprised! Yes, that's the basic point here. Calculate the power used by each load, and add them all together. I shouldn't have assumed that. I really don't know what Lei wants this information for. If he wants to know the total power consumed from the mains, then he should...
  10. KrisBlueNZ

    Measuring Sine Wave Using ADC

    This is a simple and common way to do it: The resistors must be of equal value. They divide the reference voltage in half and set the ADC input voltage so it's centered around that voltage. So when no signal is present, the ADC should read half-scale. The resistors should be 1% or better. The...
  11. KrisBlueNZ

    Assembly statements

    Yeah, I wasn't trying to be picky! Edit: pun not intended! I should have said "argumentative". Yes, that's what I mean. The caller can put a return address, or a reference to the return address, in a static variable and jump to the function. The function can "return" using, for example, an...
  12. KrisBlueNZ

    Assembly statements

    I was thinking of methods of "calling" a single bit of code without using the stack, so you don't have to duplicate the code at all.
  13. KrisBlueNZ

    Basic 555 timer

    Pfft. That's not very good. I'll try to figure it out from the photographs then.
  14. KrisBlueNZ

    Need help with relay calculation

    You're talking about the power going into the power supplies, so that would be 14W at 230V AC. But with most power supplies, the input current waveform is not the same shape as the voltage waveform. The voltage waveform is a sine wave, but the current waveform is not. Here is a good illustration...
  15. KrisBlueNZ

    Assembly statements

    There are other ways...
  16. KrisBlueNZ

    Basic 555 timer

    Did the kit include a schematic diagram? If so, could you post that as well please?
  17. KrisBlueNZ

    Basic 555 timer

    Is the door latch solenoid polarised? It may have a diode built in to absorb the back EMF. Try connecting it the other way round. Can you post a link to the timer kit you built? And a photo of each side?
  18. KrisBlueNZ

    Help with Varactor Diode

    With a 100k series resistor, it won't make much difference, no. I didn't actually suggest using a series resistor. My suggestion was to apply the control voltage straight to the capacitor. This avoids any effect on the Q of the tuned circuit. With a 100k resistor, that effect would only be tiny...
  19. KrisBlueNZ

    Need help with relay calculation

    The other power used by the circuit is drawn from the 230 VAC mains supply. The way you have wired it, the bottom lamp is powered all the time, and the top lamp is powered when the relay closes. They are not connected in parallel as stated on the diagram. Each lamp has a box that represents a...
  20. KrisBlueNZ

    Need help with relay calculation

    I've fixed the ALL CAPS in your post. This is bad netiquette. It's as if you're SHOUTING at us. You've practically answered your own question. The relay coil has a resistance of 160 ohms. Using Ohm's Law you can confirm that at 12V, it will draw 75 mA: I = V / R = 12 / 160 = 0.075A = 75 mA...
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