izach

hi stuee i am sorry still trying to fing the damn thing give me some time i will find it here somewhere.. ian

yes you are right sorry for the wrong info but i did state that smartsarah2003 should expriment with different values

basically it vibrates the molecules at microwave freqency which in turn generates heat

if you take one wire from the normal speaker and connect it to one side of a 1uF electrolyic cap then take the other side of the cap and connect it to the tweeter then take the remainig lead of the tweeter to the remaing lead of the normal speaker experiment with different values and you will see how itr makes a difference.

a/d = analogue to digital therefore to convert analogue to digital one would sample the analogue signal a given number of times each time a sample is taken a digital byte is recorded represented by ones and zero's depending on the resolution this word could be 8 bits or 14 bits etc long this would then be supplied at the output either parrallel or serial. pwm=pulse width modulation this would be an output from say a microprocessor where a square wave is generated with a varying on time and a varying off time but the amplitude of the wave remains the sames

a down counter take a predetrmined number and subtracts it one by one over a predertermined time. a zero detector usually detects the balance in wheatstone bridges a pulse generator will generate a pulse of predetermined width and amplitude

usually the volume control is in the pre-amp section varying the gain of the first amplifier. the most simplest way to get rid of the loe frequency's is to put a cap of 1uF in series with the tweeter. plse note this is the meanest and simplest way.

is the motor dc or ac

the circuit here with is realatively simple all that has to happen is an input on the pic is brought low the pic senses this and changes the lights accordinly. in the circuit R1 pulls the input high all the time while sw1 is not short when sw1 is short due to the magnet passing it i will pull the input low this is sensed by the pic. pic_magreed_switch.pdf

here is how i see it but still does not explain the pot in the 'wrong' place the op amp is connected as an open-loop differential amplifier or voltage comparator, and it s action is such that its output is driven to positive saturation if its negative terminal is more that a few hundred microvolts negative to the positve terminal and is driven to negative saturation if its negative terminal is more than a few hundred microvolts positive to the positve terminal. with this in mind the thermistor is a negative tempreture-coefficient device so its resistance falls as the tempreture rises. in practice one would see the pot in the voltage divider and not the stable reference voltage. and thus the pot would be adjusted to balance the bridge, in this conditon there would be zero volts difference between the positve and negative terminals of the op-amp. consequently when the tempreture rises above the trip level the bridge goes out of balance in such a way that the negative terminal of the op-amp goes negative to the positive terminal and the op-amp is then driven to positve saturation. therefor i cant see the thermistor warming up as there would allways be a resistance in the voltage divder consisting of the 'balance resistance' pot and the ntc. any comments ?

a circuit for which one would you like 1 2 or 3 ?

in my day i did a little monitor repair and i made this circuit using buffers and it ran 24 monitors i look around and see if i can find the drawing somwhere in my attic failing that i maight be able to find the actuall device and rip it apart to see what i used just cant remember.

since you are working with a pic there are a number of ways one could solve your problems !) inductance pick up: your emergency vehicle could have a magnet connected under it , a reed switch could be positioned under the "road surface" when the emergency vehicle passes the reed switch it will pull a input on your pic low an the traffic light will change. 2) rf transmission: your emergency vehicle transmits a rf signal to the robot"aerial the reciever pulls a input on your pic low and the traffic light changes. 3)ir : your emergency vehicle transmits a coded ir signal that is picked up by the ir sensors on the side of the road(the ones that tell a car is there) this code is decoded by your pick and if the signal is correct it will change your lights.. but for all intense and purposes i think the first one will do for your project

one thing i noticed about this circuit is the fact that the pot was placed on the usually fixed potential divider there for no stable reference voltage would appear at the input. usually one would have a stable reference voltage to work with then adjust the temprature dependant voltage this would cause a more linear under temprature switch. the two potential divders ie the temperature_dependant voltage divider and the reference voltage divder are connected as a wheatstone bridge any coments on the reason for the pot in the reference voltage??

maybe this is stupid but has no-one thought of adding a little salt to the water to make it a little more conductive. instead of using transistors for this is possibly just a small project. so try using the said battery conecting the globes up the way you need to and put the probes into the water then add the salt and stir. sound like a cooking recipe