Alimentator PWM analogic

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same doesnt drop at all....and one reading to add is 6.6mV of consumption of all circuit at 14v

take a notice... we have 1n4007 diode at output maybe this element blocking current...and voltage stay on high lvl ??
 
The 1N4007 diode performs the protection of the PWM device against any reverse voltage spikes issues by the electric motors in operation. It is corectly connected, with the anode to the collector of BD651 and with the cathode to the VDD terminal, thus in "anti-parallel" with the inductive load which consists of the locomotive motors.
In order to solve the mystery of the output 14V voltage that does absolutely nothing to motors or lights, let's try something a little radical, to see how BD651 performs. Place on the floor some rails in a straight line (not on a table, but on the floor - you will see next why). By means of two crocodile clip cables, connect the voltmeter to the rails and leave it there, then place one locomotive on the rails. Read the voltmeter and check the locomotive. If the voltmeter keeps showing something like 14V and the locomotive still does nothing, then take another cable with crocodile clips, clip one to the GND terminal and touch the collector of BD651 with the other clip (do NOT clip it there!!!). This will temporarily bypass BD651 and R3, allowing all VDD voltage to be applied to the rails. Because of this bypass, the voltmeter will show the voltage of the non-stabilized power supply, and the locomotive will start to run forward or backward at full speed and the lights brightly lit. The 16-17V voltage is a little too much to be steadily applied to the locomotive, so, as I was saying, just touch the BD651 collector with the another clip and quickly remove it when the locomotive starts running. If the locomotive runs only when BD651+R3 are bypassed, it means that BD651 is blocked or R3 is burnt, which allows very small current to flow through the locomotive on the rails.
 
@PrinzEugen your digital multimeter is capable of reading frequencies? if so please check to see if you have those 25 Khz at the gate 11 of the 4093. If so it means that your generator is working but gives very narrow pulses which are insufficient to move the motors or light something. Usually on Digital and analog multimeters have no way of showing instant voltage swing . For that you would need an oscilloscope in order to trace the actual waveform. So the instant voltage read with a multimeter will be between 12-14 volts on the rails because the circuit is working but gives narrow pulses . you will never see a voltage swing with a multimeter at this frequency. you have to investigate why the oscilator is not working corectly when you change the position on the potentiometer.
 
thank you mate...i ll try when get home your first and second suggestion...

here is reward fo your consideration and cooperation if you already find about it...

http://www.farposst.ru/phpBB2/viewforum.php?f=12

or with blog preview

http://www.farposst.ru/category/techno

lots of kalmbach books about model railways.....and misc. modelling
Detailing Diesel Locomotives

Steam Locomotive Projects & Ideas
The Complete Book of North American Railroading
Hornby Magazine Yearbook no 1 No 2
Basic Model Railroading Getting Started in the Hobby
American Passenger Trains and Locomotives Illustrated
Coal Trains The History of Railroading and Coal in the United States
Railroads Across North America An Illustrated History
Vintage Diesel Power
Modeling the '50s The Glory Years of Rail....and lost of more
 
if i understood right...

on first suggestion i just short circuit temporarily

GND and COLLECTOR of BD651 darlington


on second suggestion i use Freq. measurment of pin 11 and ground?
 
@PrinzEugen
first as mpursu said you temporary short circuit the PWM generator formed by cd4093 gates and apply power directly to darlington. in this way you check correct functionality of the output stage.
secondly you check if the oscillator is really working and generating those 25 khz needed to drive the final stage.

as far as i understood from your dialogue with mpursu it seems that the PWM generates short narrow pulses only indifferent from the posistion of the POT. since you have a stable voltage of 14 volt on the track there can be two issues as mpursu said before,

a. faulty r2 which can resutl in poor opening of the darlington
b. problem in oscilator it oscilates on a fixed frequency but with a duty cycle around 0-2%.

as ai have seen this oscillator schematic before it should work.

i will try to replicate the schematic this evening and see if i encounter the same problems you have.
 
Thank you for the completions, Oilen! :aplauze:
PrinzEugen, first of all you must check the functionality of group BD651+R3+BC547 (power section), then the functionality of CD4093 (signal section) and so on, according to what you find during tests. I was going to tell you all these, but... step by step :D
I see 3hree steps to check the BD651+R3+BC547.
First you temporarily bypass completely BD651+R3 by connecting the BD651 directly to GND, to see if the full VDD voltage is fed to the rails.
Then you remove the bypass, disconnect R2 from pin11 and temporarily connect R2 directly to pin14, which is the V+ voltage of CD4093. This should completely open the darlington BD651, and the locomotive should run at full speed with the lights brightly lit. If the locomotive doesn't behave like this, then there is something wrong with R2 or BD651 or R3 or BC547.
Then you check the overload protection. Remove any train from the rails, set the multimeter as a 10-20A unfused (yes, you saw right) and touch the rails with the testers. This will be seen by the device as a shortcircuit, which will raise the voltage drop across R3 up to 0.68V, BC547 will open and pull down the BD651 base to GND, BD651 will close and won't let through a current greater than 1A, and this is what you will read on the ampermeter display. It is a little rough :fluierat:, but this is how the overload protection works. Or you can try to place across the rails a 1 - 10ohm power resistor in series with the 10-20A unfused ampermeter, to make it softer for the device.
 
oilen a spus:
i will try to replicate the schematic this evening and see if i encounter the same problems you have.
Click pentru a extinde...
Good luck! :aplauze:
We are all very curious about your results. It shouldn't be a problem for you, as we know about your digital lighting of the Heris couchette coach 8)
 
@mpursu thank's. it's finished. I made the final circuit last evening and i never got to make pictures. Tonight i will endeavour in a more complex device. A DCC/ANALOG booster. a RS485 chained power booster for ANALOG/DIGITAL control. same hardware can be used for both digital and analog control of railroad, signals, turnouts,etc. I'll post the project in the Automatizari section.


thank you.
 
ok...here are results....

ive changed R3 and R2 resistors with 1W carbon. measured old ones and their values are ok...resistor old ones are good. tried circuit with new ones but still nothing...then went to MPURSU testing

first test....GND and collector BD651 short bypassed...motor runs...fully at 14v..pot is still useless..so clean input as output

second test.....removed bypass...R3 1W went to 14 pin....nothing....engine dead as duck....


freq. test.....at pin 11 and GND readings are about 23 khz on max.and about 18 khz pot at min


overload test didnt perform...so my conclusion is after ive changed resistors and bc543.......Darlington BD651 needs to be replaced or IC4093 ????


whats is substitute for BD651...can i use TIP120 http://www.fairchildsemi.com/ds/TI/TIP120.pdf
 
Due to these results, now we know that the power section (transistors) was defective, and the signal section is OK 8)
For the time being, forget about the transistors and disconnect R2 from pin 11. Take one LED and connect it with the anode to pin 11 and the cathode in series with an 1kohm resistor to GND. Now rotate the potentiometer. You should see that the LED light gets brighter as you go from "min" to "max" and gets dimmer as you go from "max" to "min". This will tell us for sure that CD4093 emits correctly the desired PWM signal.
Then we will deal with the transistor power section.
 
r2 removed completly,,,long lead anode into pin 11...short lead with 1kohm to ground...it light but pot is dead no min or max ...no dimming
 
pot is tested ...readings are on two pins about 100kohm and when you turn on to other side two other pins shows exactly...
 
Hmmm.... :?
As the pulses go wider ("max"), the LED should light brighter, and as the pulses go thinner ("min"), the LED should light dimmer. If the LED light does not vary as the potentiometer is rotated, then it may seem that one of diodes D1 or D2 is defective. Cut off power, disconnect D1 anode and D2 cathode from the potentiometer and check both diodes with the multimeter.
 
pot is ok....resoldered...shows 100k resistance betweens two pins ...min - mid....and max - mid no contact loose


when led is active output voltage is 3v and with pot you dim led ..but voltage stays same..3v on output... .do you think this is ok...i just control current with pot in this case
 
3V at pin11?!? :confused:
This voltage is waaaay too small, if CD4093 is fed with stabilized 9V. Please confirm that you did not connect the LED alone between pin11 and GND, but in series with an 1kohm resistor. The voltmeter connected between pin11 and GND should show something like 9V, more or less stable because of the thinner or wider PWM pulses.
 
yes led is connected with 1kohm resistor in series of course....pin 11 and gnd...voltage is guess 5.8v at max(3volts drop on led 5mm)....and at min 0V


on output ..i mean out+ and out - on scheme
it says 3 volts at max, but at min still 3v

maybe faulty transistor some how droping voltage or l7809cv
 
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