Diode question

[Ziddik]

I am assuming the 'none' means a very high resistance value.?

No eric, the diode doesn't conduct in reverse mode, so assuming the diodes are ok, btw, is Peak voltage dangerous to an equipment which needs 12v but powered using a 12V transformer and total =16V peak voltage? ..

 

[Ziddik]

Hi Zid,

When is the last time you had it working with the 1N4007 diodes?
I ask because now that i think about it, maybe you shouldnt be doing it this way anyway because the peak voltage is going to be a lot higher than 12v and things that run on a near perfect 12vdc often dont like to get banged with much higher peak voltage.
Also, where are the filter caps? Im a little surprised it worked at all with ANY diodes really.

hi mrAL, the 1N4007 Still works good, i don't know what wrong with these 6A4 diodes are.. It is printed "6A4mic" on the diodes,

 

[Ziddik]

is Peak voltage dangerous to an equipment which needs 12v but powered using a 12V transformer and total =16V peak voltage?

 

[ericgibbs]

is Peak voltage dangerous to an equipment which needs 12v but powered using a 12V transformer and total =16V peak voltage?

hi Z,
The calculations show this.

With a 12V RMS secondary voltage full wave rectified with a diode bridge circuit will charge the smoothing capacitor to 12V * 1.414 , minus two diode voltage drops.

So thats 12V *1.414 = 16.968V peak, say 17Vpk, minus 1.4V [diodes] =15.5Vdc peak.

Depending upon the current rating of the transformer, the value of the smoothing capacitor and the current drawn by the load, the capacitor could average between approx 14V to 15V.

So if the load species a 12V input voltage, a higher voltage could cause damage.

Post a picture on how you have the diodes connected to the transformer and smoothing cap, show the cap value..on the drawing.

 

[Ziddik]

hi eric, this is how i connected th diodes

**broken link removed**

 

[BrownOut]

I think you're capacitor might be connected backwards???

 

[Ziddik]

hi brown, no, the 0V is connected to capacitor's "-" pin, hope the circuit is ok.

 

[BrownOut]

Try this: remove the capacitor and measure the output voltage using a DMM set to "DC volts." It should read somewhere around 12V. If it doesn't, measure the output of the transformer using "AC volts." That should also read around 12V. If those readings are correct, try another capacitor and pay very close attention to the polarity. If you have say a 10 ohm resistor of 10 watts or so, try to substitute it for the capacitor. Take your measurement quickly then turn off the power before the resistor gets too hot.

 

[Ziddik]

oh no!, sorry guys, that was the problem of my transformer! Its output wires were loose and now completely pulled out, i will use another one, thanx brown,eric,mral,dragon n all