electronic advice regarding this device

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Sailingsaves

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https://youtu.be/Fz2knBNQSqU

The video shows an LED driver from CPC Farnell

http://cpc.farnell.com/pro-elec/gde-30c070z3/led-driver-30w/dp/LA05178

The 7W drivers give a constant 25 Volt output that I kick down to use on LEDs.

The 12W, 22W and 30 W drivers all give a pulsating output voltage. Do you think is normal?

Thanks for any responses.

I have talked to CPC (a company that up until recently I used to recommend). Their tech advisers give conflicting info. The burned out in-line RCD that failed (and 2nd one failed too), cpc said could be dry solder, then try replacing resistor, but over 1 year old so we can do no more than that. They don;t stock it anymore but sell a different one. All Pro elec branded equipment.
 
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These are constant current devices, attaching active componets to thier output is not a good idea. Did I see you attaching a dc-dc converter to the unit?
There is no "normal" behaviour in this situation
 
Dougal Tolan said:
These are constant current devices, attaching active componets to thier output is not a good idea. Did I see you attaching a dc-dc converter to the unit?
There is no "normal" behaviour in this situation
Click to expand...

You did indeed.

A 7W transformer kicks out 25V at a constant 300mA. I connected it to a dc to dc step down converter to give me 3.5V to power some LEDs (in the kitchen) in parallel. Works a treat.
Measuring the output of this transformer with nothing connected gives a constant 25 V output.

The higher wattage transformers all give3 fluctuating voltages with nothing connected at the output but a multimeter. Connect an LED strip and the strip will flash. Connect four 10 W and 12V LEDs (in parallel) with a resistor, it will flash too.

I don't understand 240 Volt things.
 
nigelmercier said:
It is either a fixed 25V, or 300mA. It can't be both. I think you are trying to connect devices together which will fight.

The flashing means it is overloaded.
Click to expand...

Thanks, yes you are right.

I should have said it kicks out up to 25V and is constant 300mA

But what I don't understand is the small 7W transformers (up to 25V constant 300mA) show a steady 25V DC (with multimeter) and no load,
but the 12W, 22Ww and 33W transformers all pulse the voltage as seen on the video (even with just a multimeter = no load) across the output.

I think they are faulty. CPC say no. But then they also say the 12V Gel acid sealed deep discharge battery I bought from them made by CamdenBoss should only be charged to 12V and discharged to 11.5V, but CamdenBoss say charge to 12.7 volt or more and only discharge to 12.4V (for longevity of batttery - gauranteed for 12 years).

The tech guy that has been emailing me keeps contradicting himself regarding the transformers, so I thought I'd ask the real experts.
 
A constant current supply means that within a certain range 21 to 43 volts I think the voltagte will be varied to ensure that there is a constant current. In effect a 43 v supply that is fed to the load. If there is no current drain then you get 43 volts out. When you start to draw the 700ma load then the output voltage will be adjusted to ensure 700ma flows. Hwever if you try to draw too much current (too much load) then the max 43 volts will start to fall due to the failings of the capcity of the supply.
These are designed to feed a number of LED diodes in series. At typical 3v volt drop of each diode it can feed a max of 43/3 or about 14 diodes in series. Any more and it will not provide enough voltage for the proper current. It can also feed as little as 7 LED diodes in series at 700ma. Any fewer diodes and the supply will not be able to limit the current to 700ma.

Now a constant vopltage regulator takes whatever voltage it can get within a range. It will produce a constant voltage regardless of current up to the max limit. It is not suitable for driving LED diodes because a LED diode takes as much current as it can get to destruction if it is not current limited. So they need a series resitor at least to limit current if running on a constant voltage supply.
To run a constant voltage regulaor on a constant current supply means that if the voltage of the constant current supply varies from the max 43v down wards with current drain the constant voltage supply will have to increase the input current to provide the same power. This incresing current will tend to cause the output voltage to rise so reducing the input current. The 2 chase one another in that pulsing fashion the rate of which depends on the size of the filtering capacitors in both out put and input circuits.
OP has definitely got his power supply/ regulators confused I hope this might explain a little olewill
 
Thank you for your reply.

Could you explain why a 7W constant current supply gives a digital mutlimeter reading (no load therefore) of 26.3V steady with no fluctuations

yet the 12w, 22w and 30w constant current supplies give a digital multimeter reading reading of 49 Volts down to 30 volts in a pulsating fashion?

This I don't understand. The rest of your explanation is excellent thank you.
William_H said:
A constant current supply means that within a certain range 21 to 43 volts I think the voltagte will be varied to ensure that there is a constant current. In effect a 43 v supply that is fed to the load. If there is no current drain then you get 43 volts out. When you start to draw the 700ma load then the output voltage will be adjusted to ensure 700ma flows. Hwever if you try to draw too much current (too much load) then the max 43 volts will start to fall due to the failings of the capcity of the supply.
These are designed to feed a number of LED diodes in series. At typical 3v volt drop of each diode it can feed a max of 43/3 or about 14 diodes in series. Any more and it will not provide enough voltage for the proper current. It can also feed as little as 7 LED diodes in series at 700ma. Any fewer diodes and the supply will not be able to limit the current to 700ma.

Now a constant vopltage regulator takes whatever voltage it can get within a range. It will produce a constant voltage regardless of current up to the max limit. It is not suitable for driving LED diodes because a LED diode takes as much current as it can get to destruction if it is not current limited. So they need a series resitor at least to limit current if running on a constant voltage supply.
To run a constant voltage regulaor on a constant current supply means that if the voltage of the constant current supply varies from the max 43v down wards with current drain the constant voltage supply will have to increase the input current to provide the same power. This incresing current will tend to cause the output voltage to rise so reducing the input current. The 2 chase one another in that pulsing fashion the rate of which depends on the size of the filtering capacitors in both out put and input circuits.
OP has definitely got his power supply/ regulators confused I hope this might explain a little olewill
Click to expand...
 
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nigelmercier said:
If you open circuit (or overload) a constant current device it will still attempt to maintain the design current. To do this the voltage will fluctuate, until it goes pop.

Each device will have a specific load range that it is designed for, anything outside of this range will cause it to fail.
Click to expand...

Many thanks.
 
nigelmercier said:
If you open circuit (or overload) a constant current device it will still attempt to maintain the design current. To do this the voltage will fluctuate, until it goes pop.

Each device will have a specific load range that it is designed for, anything outside of this range will cause it to fail.
Click to expand...
Some of them sense they don't have a legitimate load and shut down for a bit.
They are designed for a particular load and may have soft start circuits which only work with the intended load.

Using such things outside their design parameters can have all sorts of effects.

It's common to put the LEDs in series to keep the current through each the same. They may not share properly in parallel.
 
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