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  1. KrisBlueNZ

    Making two if Statements work at the same time

    You have omitted the closing brace from your first if() block, so the second if() block is actually part of the else clause of the first block. if(state1==0) { digitalWrite(pump1, HIGH); } else { digitalWrite(pump1, LOW); } <----------------- you need to...
  2. KrisBlueNZ

    pnp switch problem

    That idea will work, but Q2 will need more than 1 mA base current. The 2N4403 (the Fairchild one, anyway) is specified with a minimum hFE (current gain) of 100 at 150 mA collector current, and only 20 at 500 mA collector current. The typical characteristics graph shows that typically, the...
  3. KrisBlueNZ

    Scoreboard project

    In that case I suggest you use the CD4033 (see http://uk.mouser.com/ProductDetail/Texas-Instruments/CD4033BE/?qs=sGAEpiMZZMtdY2G%252bSI3N4T1SYayRwwFD7laTHao%2fMNU%3d). One for each digit, so 5 in total. I suspect you may regret not having a count back button, but omitting that button means you...
  4. KrisBlueNZ

    Scoreboard project

    Hi there and welcome to Electronic Point :-) Tell us your requirements and we can be more specific. How many digits per team? In other words, do you need 0-99 or 0-999? Is the period just a number, like 1~4? (Sorry, I'm not a sports fan.) How do you want to control the numbers? A button that...
  5. KrisBlueNZ

    Transistor as a switch

    It still wouldn't be anything like enough current to bias a single transistor enough to switch a relay.
  6. KrisBlueNZ

    Light following robot

    OK, this circuit should do what you want. It uses two power MOSFETs, controlled by the LDRs. I've suggested a couple of type numbers that are available from Digi-Key, but other types may be suitable as well. Go for N-channel MOSFETs in TO-220 packages, rated for at least 20V VDS voltage and at...
  7. KrisBlueNZ

    Light following robot

    There's no such thing as a "standard" motor. How much current do they draw at maximum speed and at half speed, while dragging your robot?
  8. KrisBlueNZ

    Light following robot

    Hi there and welcome to Electronics Point :-) Your 30Ω resistors are far too low, and you won't be able to use a single BC547 to drive each motor - you need much more current gain than that. Probably a couple of MOSFETs would do the job. They might need heatsinking. How much current does each...
  9. KrisBlueNZ

    Transistor as a switch

    Hi dondon and welcome to Electronics Point :) So you want your circuit to activate the relay when the LDR is in darkness (resistance approximately 1.5 MΩ) and deactivate it when the LDR is illuminated (resistance approximately 160 kΩ). You can't do this with a single BC547 because its hFE is...
  10. KrisBlueNZ

    Resistor value identification

    That doesn't quite make sense. Assuming you have a 3.5 digit multimeter, when you set it to the 2 kΩ range, it shows a value between 0Ω and 1999Ω, with no decimal point. It could indicate 565, without the decimal point, i.e. 565Ω, in which case the resistor may be supposed to be 560Ω. On the 2...
  11. KrisBlueNZ

    Resistor value identification

    We may be able to estimate a suitable value for the resistor if we can reproduce the design. To do this, we need clear, clean photos of both sides of the board. You need to: Move all the wires so they don't obscure any components Clean both sides of the board - start with a toothbrush and a...
  12. KrisBlueNZ

    Tips for learning recursion?

    Good points there in post #4, Merlin3189. Recursion doesn't scale down well. Here's a general overview of stacks and recursion - stuff that Merlin3189 already knows, and chopnhack may also know most of this as well. In order to implement recursion, some kind of stack is needed. A stack is...
  13. KrisBlueNZ

    Resistor value identification

    That resistor has obviously been running very hot for a long time. I wouldn't trust any of the colour bands to be their original colours, except perhaps the green one. Measure it, but unless it's within say ±10% of a value starting with 5, its measurement may be wrong as well. If you post some...
  14. KrisBlueNZ

    Sony XE-700 graphic equalizer/spectrum analyser

    Hi Gary and welcome to Electronics Point :-) I can't find a service manual for this product for free download. There are dozens of hits for CDP-XE-700 which is a home audio CD player, but not for the XE-700. There is one available at...
  15. KrisBlueNZ

    Dual controlling of a Relay

    You can implement the manual override in the Arduino, unless you want the override to override the Arduino if it fails. The Arduino only needs one control output for the relay, and one or two inputs for the manual override switch. Then you can implement whatever logic you want for the manual...
  16. KrisBlueNZ

    External Monitor Project...need help

    Do some experimentation. For example, create a bootable Linux CD and see if that comes up in 1366x768 graphical mode on your external screen. If it does, search the Windows knowledge base for HDMI-related issues. (I assume you're running some kind of Windows on your laptop; you didn't say.)...
  17. KrisBlueNZ

    Need help Transistor Touch Sensor

    Personally I would try that and see how it goes. Use the battery's internal resistance to limit the LED current. Just connect a pushbutton between them. If the LED is a lot brighter than you need, add a resistor - try 10Ω to start with; increase if the brightness is still too high and vice...
  18. KrisBlueNZ

    External Monitor Project...need help

    Well... there's an incompatibility.
  19. KrisBlueNZ

    Trying to repair a shaver charger

    It's pretty rough because the diode VF varies somewhat with IF and there is no defined end-of-charge condition. Diode VF(typ) also varies slightly with manufacturer, but is generally around 0.8V at 100 mA and 0.9V at 500 mA. Ideally you want the charge current to taper off fairly sharply as...
  20. KrisBlueNZ

    Need help Transistor Touch Sensor

    Hi there and welcome to Electronics Point :-) You seem to think that because these numbers are the same, that you can connect them together and they will work. That's not necessarily true. Those numbers are voltage and current values, but they mean different things for the LED and for the...
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