Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
yes..the frequency is close to what you said, to be exact it is 1.4KHz, i haven't noticed but i guess the components
have some tolerance, the battery i want to desulfate it is not a total mess, it can hold a charge but after one day it
can no longer feed a starter, it is only able to turn one lights and stuff like that.
yes..the frequency is close to what you said, to be exact it is 1.4KHz, i haven't noticed but i guess the components
have some tolerance, the battery i want to desulfate it is not a total mess, it can hold a charge but after one day it
can no longer feed a starter, it is only able to turn one lights and stuff like that.
Caps are as much as +/- 20%
Most resistors today are +/- 5%
Rarely does a battery in a car Go Sulphated, Unless it sets for 2 or 3 Months Unused OR your Alternator is Not Charging it Properly.
Most Alternators put out about 14.5 Volts.
CHECK YOUR!
What you wrote Above: can also be a BAD Cell.
If it has caps on each cell, Use a Hydrometer to test the cells.
A Sulphated battery will measure LOW readings, but about Equil readings Between All Cells.
A battery that is BAD will have most cells reading good and about Equil, but one or two, reading really Poor or bad
hi again, thanks for your advices, although i have already look at these details for the alternator and it outputs 14.4V
i'll look at it again just in case it doesn't any more, other than that...the battery is almost 5 years old, and usually after
so long time, depending their quality, they might start to fail, mine it's a Bosch Silver 4CH, it served well all this time
period, but last year it was indeed unused for a month or two.
concerning the circuit i think i've managed to make it work, looks like it was a loose connection on top above
the 47nF capacitor, now i can hear the switching noise from the coils and i can measure frequency which is about 500Hz
on the bettery poles, i guess the reason that the incorrect frequency it's the a wrong coil i'm using...which is 1.2mH
instead of 1mH though i'm not sure if that's the reason..or maybe something else...
5 Years Old:
That is about the Normal Life Expectancy of Most Car Batteries.
Probably won't work, But Good Luck on trying to restore it.
The Frequency of Oscillation is Totally Dependent on the Two Resistors and the cap on the 555 (pins 7, 6 and 2)
The Mosfet and Chokes Just produced a Higher Voltage Spike.
If frequency is 1400Hz then the current will rise to around 5A at the peak (more if the inductor saturates), so the average current will be 2-3A. That's too much for 100mA rated inductor. You need an inductor rated at 5A or more.
hi, measuring again the frequency at the pin #3 of the 555 seems to be 2.4KHz and at the output on the battery seems to be 500Hz
i think the frequency changed when i connected the coils, etc..also i added a 5A fuse and it doesn't gets blown, nothing gets hot...
[EDIT]
i've changed C2 to 22nF and the frequency at pin #3 went lower and the 1mH inductor started getting hot, measuring again the frequency on the battery it's different than what it is on pin #3 also seems that the pulses of the desulfator aren't more than 100mV meaning it doesn't do what it is suppose to do... (unless if i measure wrong..) i don't understand what's going on...
First off you should not be trying to make this on a bread board. They may be fine for digital stuff but they are vary unpredictable for analog stuff.
You should at least take your high power components off it and solder them together in open air.
First off you should not be trying to make this on a bread board. They may be fine for digital stuff but they are vary unpredictable for analog stuff.
You should at least take your high power components off it and solder them together in open air.
i'm about to build it on a pcb, but first i wanted to do some tests, do you have any idea why the frequency is not the same on pin #3 and on the battery?
Your FET is not turning on and/or all the way. It maybe a bad connection with the high power parts on your bread board.
Take them off and solder them together.
The Signal at the Battery is Being LOWERED in VOLTAGE Because of the Batteries Low Impedance.
The Coils do Not change the Actual Frequency, But they Highly Distort the Waveform.
So your Frequency Counter is Probably NOT Giving a Correct Frequency Reading at the battery.
You need an Oscilloscope to really see what is happening.
The Frequency you get at Pin 3 Is the Actual Frequency.
4pyros, I Only Build Analogue stuff and I have NEVER had any problems using Breadboards or on any measurements on them.
I looked at the 555 circuit and it is supposed to be on for about 750 us, then off for about 33 us, so the pulses where inductor is on are only 33us in duration, during which time the inductor's current should increase only to about 400mA. In theory, this should be fine. So, 5A rating that I suggested earlier might be an overkill and the inductor rated for 600mA - 1A should be fine, but the 100mA inductor would definitely saturate. If it saturates, you get high currents and something will go.
Another question is whether you get the 95% duty cycle that it is supposed to produce at pin 3 or not? Can you measure the duty cycle?
As a quick fix, I would try decreasing R2 to 10K and then further to 4.7K. This would make "on" pulses shorter while keeping the frequiency, so you can get away with smaller inductor.
I wouldn't change the capacitor. It's probably chosen to set the frequency believed to be good for the desulphation.
Quite a bit actually. I had a triac circuit which I tested to control the speed of 1200W fan, so it would be about 10A. I only did it for couple minutes because the triac was getting very hot without a heat sink, but it was fine otherwise.
I have also done some circuit at or near 10 Amps with Mosfets,
But I Do Bolt Heatsinks onto the Mosfets.
Not Big ones But big enough to prevent Instant Failure.
Your FET is not turning on and/or all the way. It maybe a bad connection with the high power parts on your bread board.
Take them off and solder them together.
The Signal at the Battery is Being LOWERED in VOLTAGE Because of the Batteries Low Impedance.
The Coils do Not change the Actual Frequency, But they Highly Distort the Waveform.
So your Frequency Counter is Probably NOT Giving a Correct Frequency Reading at the battery.
You need an Oscilloscope to really see what is happening.
The Frequency you get at Pin 3 Is the Actual Frequency.
how can i be sure that it outputs pulses of about 50V and that the output frequency is indeed what pin #3 gives?
i'm using an oscilloscope, that has FFT/frequency counter but it's small around 1MHz. the frequency at pin #3 on new desulfator i've made
it's around 2.8KHz and on the battery i measure 500Hz.
the new coil i'm using is 174uH (the large one) and 1.2mH the small one, the 470k resistor is about 390k and the 22k is about 19.8k
the 330 ohm resistors are 290 ohm the C2 capacitor is 2.1nF
I looked at the 555 circuit and it is supposed to be on for about 750 us, then off for about 33 us, so the pulses where inductor is on are only 33us in duration, during which time the inductor's current should increase only to about 400mA. In theory, this should be fine. So, 5A rating that I suggested earlier might be an overkill and the inductor rated for 600mA - 1A should be fine, but the 100mA inductor would definitely saturate. If it saturates, you get high currents and something will go.
Another question is whether you get the 95% duty cycle that it is supposed to produce at pin 3 or not? Can you measure the duty cycle?
As a quick fix, I would try decreasing R2 to 10K and then further to 4.7K. This would make "on" pulses shorter while keeping the frequiency, so you can get away with smaller inductor.
I wouldn't change the capacitor. It's probably chosen to set the frequency believed to be good for the desulphation.
it's hard to measure the duty cycle...i got a multimeter that has frequency meter, but it doesn't show anything. the oscilloscope it's more hard for me to use.
Your Frequency Measurements do NOT Appear Correct.
The Duty Cycle on this circuit Might be too Short for your Freq-Counter.
It Appears Those Values are NOT CORRECT.
Most Resistors ar +/-5%
I Suspect your measuring them IN-CIRCUIT?
YOU CAN'T MEASURE THEM CORRECTLY, WHILE IN-CIRCUIT.
Remove ONE END to Test Them.
In Fact:
With 470K, 22K & 2.1nF, Frequency at the 555, Pin 3 Will be 1,336 Hz.
If 390K, 19.8K & 2.1nF, The Frequency will be 1,600 Hz.
The Low Side Duty Cycle on these is only about 4.5%
Can you Post the Waveform you have at the Battery?
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
(click on it to enlarge...)
