how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC0808

[Zohaibmaroof]

how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC0808

I am in the end of my final year project that is BLIND PERSON NAVIGATION SYSTEM

using 89S51
DAC0808
Ultrasonic range finder SRF04
LF351 op-amp
2n2222 transistor

i am just now facing a problem , i want that when a person come closer to sensor (SRF04) the vibration motor starts vibrating and when person or obstacle come closer to sensor vibration becomes more means smaller the distance between sensor and obstacle greater the vibration produce

but PROBLEM is motor just vibrate with different speeds when obstacle come in the range of sensor how do i make smooth increase in voltages which is given by DAC0808 to op-amp LF351 to make vibration according to the distance
please help me out this thing will improve me project performance and will make it more efficient

 

[BradtheRad]

Re: how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC

To alter the vibration strength, the only thing you can do is change motor speed.

Are you driving the motor from the op amp, or through the transistor? Is the op amp heating up sufficiently to cause protection shutdown?

If through the transistor, did you put the motor on the collector leg? (NPN nomenclature). Because when a motor is in the emitter leg, it can interfere with bias current flow.

Does motor surge draw enough current to cause the power supply to droop at any time? This would cause erratic operation.

 

[Zohaibmaroof]

Re: how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC

The Circuit i made is made in this way
first Sensor give signals to MICROCONTROLLER
MICROCONROLLER sends particular codes to DAC0808
DAC0808 sends 0 to 2 ma current to op amp( LF351)
LF351 produce voltages (0 to 5 volt) according to the distance from its output i have connected BASe of transistor 2n2222(NPN) because op-amp is not producing power that will drive the vibration motor and yes i put the motor on collector leg , i am also facing problem that when i place obstacle in front of sensor it gives low voltages at some particular distance .
for example i have made the limit of distance at 18 inches ( 1.5 foot), at 18 inch little vibration is produce , at 17.5 or 17. inch great vibration is produce , at 15 or 13 inch little vibration then going more closer to sensor will gives same conditions alternately , i also observer that by placing multimeter at collector leg it gives approx 1 volt at 18 inch then at 17.5 it gives 2 to 2.8 volt then after that 3 volt when placing obstacle more closer to sensor then more then 3 volts found. more or less i found that there are 4 to 5 places ( in the range of 18 inch) where my circuit is producing low voltages where it should not produce low.

 

[BradtheRad]

Re: how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC

Not knowing how your microcontroller processes signals from the sensor ...

How does your system handle repeated echoes? Sound waves bouncing back and forth between the sensor and an object a few inches away. These might create odd echo sequences at various distances.

Did you test the transistor stage separately from the op amp? Seeing if it operates properly by applying the expected range of bias currents, and watching for expected voltage across the motor?

Did you also verify that the op amp puts out the expected voltage/current? Does output V ever get pinned at the high or low supply rail? And stays there until there's a big change at the input?

Does motor commutation cause spikey noise on the supply rail? This might cause false triggers to come from your sensor unit, or elsewhere.

Does the rotating weight ever bind up inside its housing? This will cause it to draw high current until it gets going again.

 

[Zohaibmaroof]

Re: how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC

SRf04 ultrasonic range finder is a sensor which sends and receive automatically i just have to trigger its input pin (by making its trigger pin HIGH for 10 us) then sensor sends echos and make its ECHO OUT PIN high and when echos reflect back from obstacle and received then ECHO OUTPUT PIN becomes low means as long as echos are in AIR the ECHO OUTPUT PIN will be HIGH according to it

---------- Post added at 23:31 ---------- Previous post was at 23:30 ----------

89S51 has 2 timers , i am using timer 0 (timer value ,has two registers that are TH0 TL0 both register goes from 0 to 255 steps or you can say values, both registers values increase in HEX values from 0 to FF that means total values goes from 0 to FFFF or 0 to 65535 in DEC ) My sensor sends sound waves and there is a pin called ECHO OUTPUT pin which becomes high immediately after sound waves are transmitted then when sound waves reflect back from obstacle , ECHO OUTPUT pins goes low , so i made program which starts timer when echo pin goes high and stop time when echo pin goes low ,i have limit the detecting range that is 18 inch so by searching from web i found that SRF04 ultrasonic sensor takes approx 166 us to detect object placed at 1 inch , so i multiplied 18 inches with 166 us then by further calculation i found a value that is 1374(HEX) and i placed that in my program in such a way that when ever sensor gives values greater than this values then controller will not do any action or does not vibrate motors, now other thing is that when timer values are produce according to the distance longer the distance greater the timer value short distance short timer value so i found , if i send this value this would vibrate the motor directly proportional to the distance but i want inversely proportional to the distance, so i found a solution whhen timer values comes i subtract that values from 255(FF) because max value come in TH0 and TL0 registers FF this thing alter the value , for example if timer value in TH0 comes 180 then it was subtracted from 255 and become 75 that value is then transferred to DAC0808(DAc0808 is set to produce 0 to 5 volt) which produces particular voltages according to the code 75 value in this way circuit works repeatedly

 

[BradtheRad]

Re: how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC

Can't see that there's anything wrong with your method. And it's shown by the fact that it works most of the time.

The erratic operation you're getting is one of those problems that drives a designer crazy. Seems like every project has some kind of 'gotcha' hidden in it.

So near and yet so far.

When a project is made from several sections, and it doesn't work perfectly, then it means you'll have to get it working one section at a time.

Have you tried differently shaped objects?

What about a flat surface, held in such a way that infinite echoes might go back and forth between it and the sensor... does that have the possibility to cause the erratic operation?

Does a rounded object create the problem?

Is there a capacitor anywhere in the part of the circuit that drives the motor, creating an LC resonant loop?

 

[Zohaibmaroof]

Re: how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC

I want to thanks to all those people who answered my Question

Here is my FINAL YEAR Project's video which i have finally completed with best excellence .watch it out

Ultrasonic navigation System first time made in Pakistan if i am not Wrong(Made By Zohaib) - YouTube

---------- Post added at 01:47 ---------- Previous post was at 01:46 ----------

I want to thanks to all those people who answered my Question

Here is my FINAL YEAR Project's video which i have finally completed with best excellence .watch it out

Ultrasonic navigation System first time made in Pakistan if i am not Wrong(Made By Zohaib) - YouTube

 

[BradtheRad]

Re: how to drive a vibration motor(cell phones) with variable speed using 89c51 & DAC

Congratulations.

To assist the handicapped is one of the noblest ways to use our knowledge and skills.