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  1. Hi everyone, i am in desperate need of finding a 3- axis digital compass chipset. can anyone recommend the name of one such chipset BESIDES any product from Honeywell..... or even a 2-axis and 1-axis that i can combine. any help would be appreciated thanx
  2. hey guys, i got a problem... can someone give me a VERY simple circuit that allows me to switch a bp103 phototransistor on when it senses light from a standard red LED. the phototransistor is gonna be kept in a dark box with the led.when the led is off the output from the phototransistor will be 0v. when the led switches on, the phototransistor will switch on and give me around 5Volts out...the circuit is powered by 5V.. please help thanx
  3. okay, thanx but now im working with a 5volt rail, how am i gonna get a -5V for -Vs? im sorry, im pretty bad at this.
  4. Can anyone please tell me how to bias an lm35 temperature sensor to work in the range of -10 to +50 celsius? Thanx
  5. Hi there i need help with a new project of mine. i need to design a timing circuit using a 555 timer. it requires that the timer gives a signal out for a specified time. once this time has elapsed, the signal must go to 0V. all i really want to know is, how do i control the timing period of a 555 using voltage? for example: i want to give a voltage of 3V to the timer and i want the signal to stay on for 10 seconds. then, if i increase the voltage to say 5V, the signal must stay on for 20 seconds.(this is just an example). please can someone help me. it would be greatly appreciated. than
  6. try this link..i found it useful.. http://www.electronics-lab.com/projects/oscillators_timers/014/index.html
  7. Does anyone have any designs for a simple earth leakage sensing and protection device? would be appreciated thanx mike
  8. Thanx alot...sorry im a bit slow with this sort of stuff. Im using a 12V NiCd battery. IM going to have a voltage divider network accross it to provide a reference range of 0-5volts. This will then go into an a/d converter which will convert the voltage to a 8-bit digital value(0-255). This will then go to a microcontroller which will compare this value with a full charge reference value. If the values are within range of eachother then the micro will switch the charge to a trickle charge of small current. Thats why i want the switching circuit.
  9. Hi there... I really need help. I am busy designing a battery charger using a microcontroller. i need help with the attached circuit. When the battery is full i would like to be able to charge it using a far lower current. Im doing this using a simple circuit using two resistors in parralel. When the battery is charging the switch is open and the current is running through the one resistor...this gives me a large current. When the battery is full the microcontroller sends a voltage to a switch which causes the current to reduce(please see the circuit). I want to know what switching device
  10. The tests have been done in the lab. No harm comes to the motor, as long as the CO2 is sent down the right airgap. Besides, the CO2 is only supposed to be turned on once the motor gets too hot...so it doesnt freeze.....once the temp is back down to a safe temperature the CO2 switches off....so any ideas??
  11. Hi there, ive been assigned a very interesting project. I need to design a cooling system for a go-cart using CO2 cooling. Im thinking of using an LM355 temp sensor to sense the temperature on the motor. when the temperature on the motor reaches a certain threshold level, i want a transistor (or something else) to switch on causing a solenoid on the CO2 bottle to open the valve releasing CO2 through nozzles into the engine. Im quite useless as regards my circuit design. Does anyone have any ideas on how i could maybe connect the transistor to the output of the sensor and calibrate it to
  12. Hi there, Im doing a research project regarding testing a system in a controlled environment. I am using an environmental test chamber. I dont know how the thing works? Has anyone got any information regarding this. Any Datasheets, manuals or anything explaining to me how the thing works. Thanx Mike
  13. ive got another problem-maybe you guys can help me out.... im attaching a schematic of my supply so far. it works pretty well for medium loads 1k - 1000k. but as soon as the load goes quite low, like 10 ohms or lower, the output voltage stops regulating and starts to drop drastically. the current, which isnt allowed to be more than 500mA shoots right up to bout 2 or 3 A. any suggestions?!!! thanks kindly
  14. mixos, as regards the first schematic you posted for me, do you have any suggestions to what the rating of the zener diodes should be?
  15. Thanks very much guys. This stuff is really useful. :)
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