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

there are a number of ways to do this 1) a hot air pencil is a good way if you are experienced so as to not to blister the board. i use a weller wmd 3 this is a desolder station with a hot air pencil. 2) the best way is with infra red heat soldering staion with a heater bed. the heater bed warms the bottom of the pcb and then you use the infra red pencil to warm from the top this then warms the solder under the bga and it is released. to replace you have toprep the board first with solder paste using a mask then place the bga on the board an do the same as for releasing it .

this might help a little if R1=R2=R and C1=C2=C the multivibrator is then symetrical and generates square waves of equal mark space ratio then the period of oscillation is given by the formula T=1.38RC therefore the free running frequenct of such a multivibrator is given by the formula F=1/T =1/1.38RC 1.38 is 2 x 0.69 where 0.69 is the log Vo/Vt where Vo= initial voltage and Vt is the voltage after a time t THIS EQUATES TO t=RC log Vo/Vt I hope this sheds some light on the subject

managed to find a way to send the diagram goodie

hi audioguru thanks for the advice you are correct in saying this is a audio device and there is no gain at 3mhz. please inform me how to download the schematic and then i will show you how my latest design looks see if you have any suggestions many thanks IAN

two things,just to get everything straight, 1)a bd241 c is a npn device @ 3 amps 2) i am trying to build this circuit but i have realised that the max i can get the oscillator to do is 4mhz 3) working the midnight oil caused me to miscalculate my figures as i was drawing 50 watts off a 10 watt resistor. 4) wowuld love to post my drawing but i use ares lite and dont know how to convert it any suggestions. i will post it as it is quite a good sine wave generator up to 4mhz and the heating problem has beeen fixed. 5) problem is i am now trying to design a 40mhz oscillator that will drive a air coil with secondary output with 100Vpp yes 100Vpp

this is the way it works for me, go down to the stationary store and buy some photocopier(ie laser) hp photo paper copy your design onto this remembering orientation of board(you might have to mirror the copy) make the copy as dark as possible once satisfied with the copy lay it ontop of the copper with the printed surface facing the copper. using your steam iron press firmly on the back of the photo paper ironing all around the circuit print once satisfied with this using hot water and a tooth brush wash the paper backing away carefully this will leave the copy on the copper ready for etching simple hey

i have a circuit i designed using a pic to control leds to flash in different sequences if you need it i will mail it to you

please refer to remote control of electrical appliances, i have designed many circuits for control of electrical appliances thruogh computer and remotely thruogh computer please let me know what you are looking for and i will try to help

what is it you want to know about pc control of electrical appliances, is it thruogh serial port or parrallel is it many or just one do youy want remote control or wired ????

need help with a astable oscillator running at 40 mhz i am using the standard transistor astable oscillator design and feeding it with a variable voltage therefore getting a variable amplitude of 100vpp 40mhz signal problem is that after a while it heats up and dies, thinking that maybe the transistors are no good for the job using bd241c. was wondering if i could use mosfets instead ?