lamp dimmer on LED power cord?? - The Planted Tank Forum
 
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post #1 of 9 (permalink) Old 05-03-2015, 03:07 PM Thread Starter
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lamp dimmer on LED power cord??

Do people think you can put an inline lamp dimmer on an LED light? For that matter, on the power cord of a filter to reduce the flow? I'm interested in doing the filter because mine has too much flow. I'd like to know if people think it's safe, too.

This hardware uses a low wattage, 3W x numer of LEDs, not much on the impeller of a filter, and a lamp dimmer works on straight wattage from the cord, say on a filter.

An in-line lamp dimmer interrupts the power cord and has a variable voltage switch that reduces the voltage and I would think slow the impeller of a filter, just like it would dim a lamp.

Thanks for the advice.

MY TANK: Planted 10g; 2 x 10W CFL; Fluval U2 internal filter; MGOCPM/black sand cap

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Last edited by Django; 05-03-2015 at 03:20 PM. Reason: edit
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post #2 of 9 (permalink) Old 05-03-2015, 04:11 PM
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You should never use a dimmer on a electric motor! The motor will very likely be harmed by doing so. If you want to reduce the flow through your filter you can safely restrict the output of that filter with a valve. The pumps used in filters don't generate much pressure at all, so restricting the flow from them doesn't result in the pump being forced to build up a big pressure. Those pumps just move water, but at a low pressure. When you restrict the line the water flows through, all that happens is that the pump moves less water.

Dimmers that work with incandescent lighting don't work at all with LED lights. You will probably just shut off a LED light if you try to use a dimmer on it.

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post #3 of 9 (permalink) Old 05-03-2015, 05:03 PM
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Lamp Dimmers do not work on LED's or Motors so your premise is entirely flawed.

exception:Unless the LED was specifically designed to do so, like incandescent replacements that screw into traditional lighting.

a FAN SPEED CONTROLLER designed for motors MIGHT work on a pump, but more than likely will simply burn your pump up because they typically make fans emit odd noises at partial speed.


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post #4 of 9 (permalink) Old 05-03-2015, 05:11 PM
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What type of filter there are options to reduce flow easiest way is drill bigger holes if you are using a spray bar
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post #5 of 9 (permalink) Old 05-03-2015, 07:10 PM
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I don't think fan speed controllers will work on mag drive aquarium pumps. They're different than the types of motors used in ceiling fans, etc.

LED drivers have to be designed to be dimmable, otherwise they won't be able to dim no matter what. They have somewhat complicated circuitry and unless they're designed to be dimmable, they're designed to keep a constant current regardless of voltage fluctuations.

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post #6 of 9 (permalink) Old 05-04-2015, 04:05 AM
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Quote:
Originally Posted by Django View Post
Do people think you can put an inline lamp dimmer on an LED light? For that matter, on the power cord of a filter to reduce the flow? I'm interested in doing the filter because mine has too much flow. I'd like to know if people think it's safe, too.

This hardware uses a low wattage, 3W x numer of LEDs, not much on the impeller of a filter, and a lamp dimmer works on straight wattage from the cord, say on a filter.

An in-line lamp dimmer interrupts the power cord and has a variable voltage switch that reduces the voltage and I would think slow the impeller of a filter, just like it would dim a lamp.

Thanks for the advice.
EVERYTHING depends on the motor type:
Quote:
There are several types of single-phase "AC motors." Some, like the universal motor wth brushes are relatively easy to control. The capacitor-start and split-phase can be very difficult to control, and when controlled, they lose a great part of their torque. The aquarium pump is possibly a synchronous motor, in which case you should be able to control it with frequency, not pwm.

The place to start is to determine what type of AC motor you have. Search on synchronous, split-phase. and capacitor start motor to see if any match what you have. John
http://forum.allaboutcircuits.com/th...ntroller.9753/

As to the LED's it all depends on how they are driven..
Constant voltage LEd's can be dimmed using PWM to "chop" the voltage.. not change it.. nor change the current..
constant current LEd's usuallly have dimming "built in"

and ect.. ect.. many variations including current control

You need to know more specifics on any setup to determine if any of this is possible..

This will control some AC motors but is useless for LED
http://www.rakuten.com/prod/dart-con...FZRgfgodBCcA7w

https://www.anaheimautomation.com/ma...otor-guide.php

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post #7 of 9 (permalink) Old 05-04-2015, 04:22 AM
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Quote:
Originally Posted by PhysicsDude55 View Post

LED drivers have to be designed to be dimmable, otherwise they won't be able to dim no matter what. They have somewhat complicated circuitry and unless they're designed to be dimmable, they're designed to keep a constant current regardless of voltage fluctuations.
well yes and no.. All those LED strips you see are run on constant voltage..
A switching power suppy x number of led's whos V(f) is under the ps voltage and a current limiting resistor..
to "dim" them all you need is a chopping curcuit composed of simple "parts"..
By varying the voltage timing you "dim" the LED .. 12v at 50% of the time is dim..
nothing more than a high speed switching circuit using say a timing chip or mosfet..

Once you get into self contained AC driven (initially) LED "bulbs" then things get more complicated..

Simple LED dimmer for 12v constant voltage LED's

http://www.reuk.co.uk/LED-Dimmer-Circuit.htm
http://www.electroschematics.com/973...er-led-dimmer/

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post #8 of 9 (permalink) Old 05-04-2015, 03:19 PM
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Quote:
Originally Posted by jeffkrol View Post
well yes and no.. All those LED strips you see are run on constant voltage..
A switching power suppy x number of led's whos V(f) is under the ps voltage and a current limiting resistor..
to "dim" them all you need is a chopping curcuit composed of simple "parts"..
By varying the voltage timing you "dim" the LED .. 12v at 50% of the time is dim..
nothing more than a high speed switching circuit using say a timing chip or mosfet..

Once you get into self contained AC driven (initially) LED "bulbs" then things get more complicated..

Simple LED dimmer for 12v constant voltage LED's

http://www.reuk.co.uk/LED-Dimmer-Circuit.htm
http://www.electroschematics.com/973...er-led-dimmer/
Yes... an LED strip with current limiting resistors will dim, although no that well (very non-linear).

However, the OP said his fixture uses 3W LEDs. I'm pretty sure virtually all commercially sold fixtures with 3W LEDs use some sort of constant current driver, the majority of which are not dimmable unless advertised as such, AND I believe most are designed to use both 120/240V and 50hz/60hz which further makes them harder or impossible to dim.

It MAY be possible to use a PWM solid state dimmer on such a fixture. I'm not sure if it would work, and may ruin your fixture, but it may be worth a shot if you're brave.

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post #9 of 9 (permalink) Old 05-04-2015, 04:00 PM
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Originally Posted by PhysicsDude55 View Post
Yes... an LED strip with current limiting resistors will dim, although no that well (very non-linear).
PWM maintains current and voltage (relatively constant but some rampup period) but changes "period" of off/on.. There is little non-linearity
Quote:
Originally Posted by PhysicsDude55 View Post
However, the OP said his fixture uses 3W LEDs. I'm pretty sure virtually all commercially sold fixtures with 3W LEDs use some sort of constant current driv
It MAY be possible to use a PWM solid state dimmer on such a fixture. I'm not sure if it would work, and may ruin your fixture, but it may be worth a shot if you're brave.
all Beamswork 1-3W are constant voltage and easily dimmable w/ a PWM dimmer between the power supply and the light head..

but your right.. many do have constant current
Few would even consider controlling the AC side.. It is pointless..

Quote:
Alternatively, PWM dimming can be performed by quickly turning the regulator on and off. At low PWM frequencies (<1 kHz), this can still give great accuracy (Figure 10).


http://www.analog.com/library/analog...ed_driver.html
Quote:
The average value of voltage (and current) fed to the load is controlled by turning the switch between supply and load on and off at a fast rate. The longer the switch is on compared to the off periods, the higher the total power supplied to the load........................
The main advantage of PWM is that power loss in the switching devices is very low. When a switch is off there is practically no current, and when it is on and power is being transferred to the load, there is almost no voltage drop across the switch. Power loss, being the product of voltage and current, is thus in both cases close to zero. PWM also works well with digital controls, which, because of their on/off nature, can easily set the needed duty cycle.

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Last edited by jeffkrol; 05-05-2015 at 01:15 PM. Reason: edit
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