Alimentator PWM analogic

mpursu

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I confess, I've had a VERY hard week and I am extremely tired, so I couldn't understand the meaning of "just emmiter as out and vdd as input". I have said very clearly that the emitter of BD651 goes directly to GND and its collector goes to VDD via 1kohm and LED, without any mentions of "input" or "out".
 

mpursu

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So now that we know for sure that BD651 is working properly (or... that's what I think I understood :D), it's time to solder the new 7809 on the board and to reconnect R2 between pin11 and the base of BD651.
19mjbc.jpg

Carefully reconnect the 17V power supply to the upper left input wires. Now the LED should shine brighter or dimmer, according to the rotation of the pot.
 

PrinzEugen

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ive connected....emitter to gnd yes...my mistake in text...

tommorow ill replace faulty lm7809........

-----------------------------------------------------------------
i do some experiment...
i have lab power...tried directly 9v to pin 14...with 2k7 back on pin 11...without lm7809...

its ...short ciruit...:(
 

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If the 9V lab power supply, connected directly to pin 14 and GND, says "shortcircuit", this could mean only two things. Either there are some stray solder droplets between the pads where 7809 was, causing the shortcircuit between pin 14 and GND, or... all these messed-up connections and defective components have damaged the CD4093 itself :(
Clean thoroughly the above-mentioned pads, then try again. If the shortcircuit is still there, then take off the defective CD4093 and get a 14-pin standardized socket, along with 2-3 other new CD4093. Replace the old CD4093 with the socket, then reconnect the 9V lab power supply and see what it says. If everything is OK, then disconnect power, put a new CD4093 into the socket and start again. I am sure that this time there will be no more shortcircuits, and you will be able to go to the next step.
 

PrinzEugen

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i take new board....completely all new components...rechecked new 7809 regulator..no shorcuits.....ive used 14pin pad for new cd4093

all soldered and connected from original scheme...insted od BD653 used BD649 (pretty much same 90%)...

taken care of positive and negative voltage

all tests were run for 15-20 sec.


Board pluged in.....engine not workin'...even led too.... :( ...on output close to 9 volts and raising ??? slowly to 10V ??? pot useless in this case no min or max same ouput voltage...

ok...then i've tried old BD651....same thing...but output voltage is 3v. on min and max too ?????

after that ive back bd649....tried again...10volts on output...lm7809 got some heat......all disconnected....


tried third time from lab power now....lab signaled shortcircuit....lm7809 is dead..taken out all pins on new one are shortcircuited.
:(


definitely....ive do what i can...no thing has to be done...so concluison is that my scheme on split strip-board not working...something is wrong

ive trust BDA and of course you MPURSU...but in this project i have no luck...

thank you guys for help...specially MPURSU...
 

mpursu

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I'm so sorry it did not work for you, and I still can't understand why :(
If you have a friend in the neighborhood who knows electronics, ask him/her to assist you when you will try again to build this device. As you can see, I did not say "if", but "when", because I most certainly do hope that you will try again and, this time, you will make me proud :)
 

PrinzEugen

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i will search for new tested pwm stripboard scheme....this had modifications from your original scheme to BDAs to mine diagram...something is causing shorcuts and small curent and overheating of l7809cv

for this money invested ive better buy new PWM... :(

thanks anyway...
 

PrinzEugen

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same movie....same scene...third time

new components again, new board again....led dimm and shine wit full scheme

on output 14v,4 at min and 15.1 at max....20khz at pin 11...7.3v at 14 pin....

on loco ....leds shine on in both direction at same time....motor buzzing..but still dead..wont no move a bit...current problem maybe....????????????????????


same thing as i disconnect D3 diode and BC547 and R3....as i say same thing as full scheme....all components from different seller ok....
 

mpursu

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You say that all lights of the locomotive are shining and the motor is buzzing. This is two times wrong, because:
1) if all LED lights shine, it would mean that the locomotive gets both positive and negative pulses; where do the negative pulses come from?!
2) the motor is not supposed to buzz at 20 kHz, because this frequency belongs to the ultrasonic range and cannot be heard; if you can hear the motor buzz, it means that somehow it gets pulses with much lower frequency, and... where do they come from?!
What kind of power supply are you using? How is the transformer output alternative voltage rectified? Does it have filtering capacitors of large values, say 2200 - 3300 - 4700microfarad / 50V?
Have you tried to use the lab power supply to feed the device with +17VDC? Please do so and let me know what happens.
 

mpursu

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One more thing: place an 100 microfarad / 25V at the output of LM7809, with anode to OUT and cathode to GND. This will smooth some more the 9V supply that 7809 feeds to CD4093.
In order to protect 7809 from reverse currents when the power supply is disconnected, place an 1N4007 diode with anode to OUT and cathode to IN. This will prevent the 100microfarad capacitor to discharge on the OUT terminal of 7809 if the main capacitor at the output of the filtered rectifier gets discharged faster.
But first please check the power supply!
 

PrinzEugen

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HAHA...we made it :D :D :D :D :D :D ..with lab power and without bc547c andR3

with clean 12v on lab power i get at 14 pin 9V....

test results
20.81 khz on max out 12.02

24.5 khz at min out 11.68v


when i use mehano transformer with 14.4v (vf capacitor across output +- and ac-dc rectifier ).... still work but at pin 14 i get 7.4v and unstable freq. but it works....


as i said this all works without BC547 and R3...when i connect this componets...led shine a bit...just a bit...engine dead as deadman... small current i suppose...
 

mpursu

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YEEEEEEY!!! :aplauze:
Now I'm proud of you 8)
Without R3 and BC547, the device is not protected against overload :D, so I would really think that you should consider putting them back. But first please check thoroughly R3, which should be wirewound and not pellicular, of precisely 0.68 ohms. Then check the functionality of BC547. If both components are OK, then place them back on the board and try again. The locomotive should behave as you saw in my video.
 

PrinzEugen

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tomorrow ii will put them back again....but ive check resistor and bc they are ok....


it is ok that i have 11 volts at min to 12v lets say at max...not from 0-12?

second, also freq. from 20-24khz?

eventaully from mehano transformer i get 7v at pin 14?
 

mpursu

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If you get 7V at the output of 7809, which is supposed to give 9V stabilised, do you really think it is OK? :D
I think it's obvious, don't use anymore the Mehano transformer because it does not offer enough power for the PWM device, but make your own 17Vdc power supply. Find a transformer that gives 13Vac / 2A, place at the output of the secondary coil a monolythic bridge rectifier 100V / 5A and a 4700 microfarad / 50V capacitor to the output of the bridge rectifier, and you are all set, you get 17Vdc at the terminals of the capacitor. Until then, use the lab power supply.
 

mpursu

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About the fact that your digital voltmeter does not go to zero when the pot is set to "min", I remind you once again that at the output of this device you get pulses of constant amplitude & variable width and not just a continuous voltage of variable value. A digital voltmeter would tend to show something like the maximum voltage because it can't keep up with the VERY fast variations of the measured output voltage. An analogic voltmeter can't keep up either, but it shows an average value of this fast-changing voltage due to its mechanical inertia. So the analogic voltmeter would show us some indication about the speed of a motor driven by the PWM signal, because motors also tend to react according to an average value of this PWM voltage. So it seems that an analog voltmeter would be more useful here, as long as you don't read it as a voltmeter, but rather as a speedometer :)
The frequency should be stable because the sum of the charge time and discharge time for capacitor C1 should be constant no matter of the pot position, due to this particular connection of the pot. Little variations may occur because of small differences between the characteristics of the diodes D1 and D2, some asymmetry of the pot resistive track etc. So, I would say that this variation 20 - 24 kHz may be considered as OK.
 

PrinzEugen

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oh my god im putting wrong one resistor all time....for 0.68 ohms ive put 680ohm resistor...

damn i didnt know that even exist below 1 ohm resistors...they emit lot of heat i suppose...

i just have on market to buy these
1/4W 0R68
or ceramic 11W 0R68
or ceramic 5W 0R68