i've built a bridge rectifier with a Zener Voltage regulator.
12V peak secondary
3300uF Capacitor
1k ohm load
1k ohm series resistor for the zener
a 1n4728A Zener diode.
and x4 1n4002G Rectifier Diodes

the datasheet says that the zener diode has zener voltage of 3.3. i was able to get 3.2 in multism, but i'm getting a 2.8V steady voltage when i measured it with DMM,

when i measured the current going through the load with my DMM it's measuring around -0.06mA, and the value doesn't change despite switching the polarity of the probe(still negative current) is my DMM broken? or i just made a mistake in the circuit.

also i find it weird that the current on my load is so small wasn't the current supposed to be 2.8V/1k ohm which is 2.8mA because the load and zener is in paralell

 

schematic please......

 

schematic please......

https://imgur.com/QiAhnwo



ty

Moderators note: removed unnessesary info and white space

 

My bet is you’re not using your meter properly. It needs to be in series with the load. There is a fuse that could be blown. Make sure the probes are properly plugged in.

 

My bet is you’re not using your meter properly. It needs to be in series with the load. There is a fuse that could be blown. Make sure the probes are properly plugged in.

what i did was i removed one end of the jumper wire that was connecting to the load resistor then attached one of the probe with that jumper wire while the other end of the probe i connected it to the load resistor. we didn't use a few.

 

we didn't use a few.

Do you mean fuse? Most meters have an internal fuse and it's easy to blow them when measuring a current. This would only apply to the low current range (on mine it's 0-200mA), not the 10A range if your meter has one of those.

What's the voltage on your filter cap?

 

Do you mean fuse? Most meters have an internal fuse and it's easy to blow them when measuring a current. This would only apply to the low current range (on mine it's 0-200mA), not the 10A range if your meter has one of those.

What's the voltage on your filter cap?

oh, i see i see. i think i saw my meter saying it can handle only up to 400mA

my capacitor has a voltage rating of 16V while my filtered voltage is around 9.8V

ty

 

Remove R2 and measure again.
[ you reduced the initial voltage by 50% ===> U . R2/( R1+R2) ]

Picbuster

 

oh, i see i see. i think i saw my meter saying it can handle only up to 400mA

my capacitor has a voltage rating of 16V while my filtered voltage is around 9.8V

ty

Something's wrong. Your filtered voltage (across C2) should be close to the 12V peak voltage of the secondary. Maybe try measuring the AC voltage of that secondary before the rectifier. Double check the orientation of the rectifier diodes.

 

my capacitor has a voltage rating of 16V while my filtered voltage is around 9.8V

What range was your meter on for the current measurements? Does your meter have different probe connectors for measuring current?

Instead of trying to measure current, measure voltages and calculate the current.

What is the value of the filter cap? 3.3uF or 3300uF?

The datasheet specifies the zener voltage at a current of 76mA:

I used a 1N4728 in a test circuit recently, and it did not give anywhere near 3.3V at low currents.

 

What range was your meter on for the current measurements? Does your meter have different probe connectors for measuring current?

Instead of trying to measure current, measure voltages and calculate the current.

What is the value of the filter cap? 3.3uF or 3300uF?

The datasheet specifies the zener voltage at a current of 76mA:
View attachment 139127
I used a 1N4728 in a test circuit recently, and it did not give anywhere near 3.3V at low currents.

the meter that i used only has 2 fixed probes.

the voltage that appeared was 2.87V then i used ohm's law I = V/R which should give me 2.87mA, but the when i measured it its giving me -0.06ma

oh,does that mean i need to make a circuit in which theres at least 3.3V for the Zener and has 76mA flowing through it?
because what i used was Izk, so i only considered/used 1 mA of current to flow to the zener if thats the case i can see how idiot i was

ty

 

the voltage that appeared was 2.87V then i used ohm's law I = V/R which should give me 2.87mA, but the when i measured it its giving me -0.06ma

Earlier you said that your filtered DC was around 9.8V. With a zener voltage of 2.87V and a 1k series resistor, the current would have been closer to 7mA.

Set up a simple circuit and see if your meter will measure the current accurately.

oh,does that mean i need to make a circuit in which theres at least 3.3V for the Zener and has 76mA flowing through it?

No. It means that the manufacturer chose a current that represented approximately 1/4 of the rated power dissipation and characterized voltage at that current.

because what i used was Izk, so i only considered/used 1 mA of current to flow to the zener

Izk is an arbitrarily low value in the knee region. Zeners should be biased past the knee region so they operate in their low impedance region.