Full bridge rectifier

Thread Starter

nickmms

Joined Jan 2, 2014
23
Hello
I would like to use a simple full bridge rectifier circuit without any filtering to power a LED work light. These work fine with no flickering when I bench test it with a 240vac to 24vac transformer.
In our DB electrical box, we have a1000V to 24V transformer. The secondary 24V is grounded so I believe I would have to have the DC output floating.
The wires of the LED light are isolated from the LED body. The LED is mounted on our metal skid.
I believe the CB would trip (and fuses might blow) if one of the wires touched the skid frame.
I would just like to make sure the circuit is safe.
PS My 240V to 12VDC is running near max amps so I cannot tap into this.PP.PNG
Thank you
 

LowQCab

Joined Nov 6, 2012
517
There is no problem with the 24-V Secondary being Grounded
if there is no chance of contact with other Grounded structures.

You could have problems with the LED Spot-Light though.
Without knowing exactly what it's Input-Circuitry looks like,
or, at least what it is Voltage/Current, Specifications/Limitations are,
it's hard to say what it's Life-Expectancy will be
running with un-filtered, un-regulated, heavy Ripple, DC,
with a peak-Voltage of ~34-Volts.

There may be heavy Voltage-Spikes from other Relays/Loads switching on or off
that are powered by the same Transformer, which could smoke the LED-Light,
so, at the very minimum, you should add an appropriately sized
MOV or TVS-Diode(s), (or Both) to the output side of the Bridge.

A continuous 50 or 60-Hertz Strobe effect
can be very irritating and tiring over long periods of exposure.
The only ways this can be eliminated is with proper Filtering/Regulation.
.
.
.
 

Thread Starter

nickmms

Joined Jan 2, 2014
23
There is no problem with the 24-V Secondary being Grounded
if there is no chance of contact with other Grounded structures.

You could have problems with the LED Spot-Light though.
Without knowing exactly what it's Input-Circuitry looks like,
or, at least what it is Voltage/Current, Specifications/Limitations are,
it's hard to say what it's Life-Expectancy will be
running with un-filtered, un-regulated, heavy Ripple, DC,
with a peak-Voltage of ~34-Volts.

There may be heavy Voltage-Spikes from other Relays/Loads switching on or off
that are powered by the same Transformer, which could smoke the LED-Light,
so, at the very minimum, you should add an appropriately sized
MOV or TVS-Diode(s), (or Both) to the output side of the Bridge.

A continuous 50 or 60-Hertz Strobe effect
can be very irritating and tiring over long periods of exposure.
The only ways this can be eliminated is with proper Filtering/Regulation.
.
.
.
Thank you very much LowQCab. The led lights draw 2amps@24Volt and are 12-32V
I just wanted to make sure the basic set up is safe.
I will look at filtering and then regulation and as you suggested mov or tvs as well.
I will just have to make sure the LEDS I use are not the type where the -ve of the LED is grounded through the led body.
 

MaxHeadRoom

Joined Jul 18, 2013
23,092
I notice you have the 12vdc and 24vac both referenced to earth GND.
Where is the 12v GND connected to? it is not clear in the diagram.
 

LowQCab

Joined Nov 6, 2012
517
The Resistors may get fairly Hot, don't touch them while the LED Spotlight is powered-on.
Make sure they have some Air circulation.

The best setup would be to mount all these parts on a 6" X 6" piece of 1/8" Aluminum.
All the listed parts are "Chassis-Mount" and should be screwed-down to something.
.
.
.
 

Thread Starter

nickmms

Joined Jan 2, 2014
23
I just tried a buck convertor I had lying around and seemed to work ok no flickering set to 20v and draws 1.5amps on the DC
There is not much heat generated. Can you see any problems using this? easy solution for me
Probably similar specs to this one on ebay .


Features:
With a wide input voltage range from 6V to 40V, the step-down converter can accurately adjust output voltage and current.
The efficiency can be up to 96%, measured at 20A, converting 24V to 12V.
It is designed with 75V/80A large current dual MOS tube.
Input and output use high frequency low resistance electrolytic capacitor, low ripple, stable output.
Wiring is convenient with these large current 30A screw terminals.
The buck module has 2 heat sink that could enhance heat dissipation.
When there is a big difference between input and output voltage, please decrease power and current.

Specifications:
Input Voltage: 6V to 40V DC(10V to 40V is suggested)
Output Voltage: 1.2V to 36V DC
Output Current: 20A(max.), 15A(suggested)
Efficiency: 95%(24V to 12V, 20A)
Output Ripple: ≤50mV
Wiring Method: Terminal
Short Circuit Protection: Self-recovery(cannot short circuit for long time)

VO+: Output positive
VO-: Output negative
+IN: Input positive
-IN: Input negative
CV: Output voltage adjustment
CC: Output current adjustment
EN: Enable, low voltage level shut off output; suspension, high voltage level is effective

When input and output is common grounded, no-load CV output constant voltage,CC output constant current

Package Included:
1 x 300W 20A Constant Current Adjustable Buck Converter Step-Down Voltage Module
 

Thread Starter

nickmms

Joined Jan 2, 2014
23
I wish you had mentioned that to start with.
If you find it reliable, go for it.
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I only found it after your last post but thank you very much for all your help.
i will still have to test it was only about $8 ..so i wasn't sure how reliable/efficient it will be
 
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