Review: KAKU ACM-LV24 LED Dimmer, 12-24Volt, max. 75Watt
Posted: Monday 11 April 2016 0:22
A review of a "Klik-Aan-Klik-Uit" (KAKU) LED Dimmer, 12-24Volt, max. 75Watt
This dimmer is to be connected between your fixed-voltage power supply and your led strip. Usually, this kind of dimmers use Pulse Width Modulation (PWM). This one is no exception.
The specs are a bit weird. Usually, such dimmers are rated for max volts and max amps, instead of max watts. The user's manual does not say anything about amps, so this needs further investigation.
The dimmer's form factor is a small white box: 4 x 4.5 x 1.7 centimeter. It has two input terminals: (positive and negative ( + & - )), and two output terminals. The terminals have screws that hold on to the wires. The negative input and output are internally connected and serve as a common ground. There's two small holes: one with a red led and one with a learn button. Learning process is the same as other KAKU switches and dimmers without code wheel selectors.
As usual for KAKU dimmers, we can set the dimmer level in 14 stages. In Domoticz, this is translated to a percentage. Minimum brightness is 6%, one stage under max brightness is 93%. Half bright is 46% or 53%. (I'm using 46%, because at that level the Domoticz slider is approximately in the middle.
Wiring up, learning and configuring in Domoticz is a breeze, if you have a good 433MHz tranceiver connected. I did not test how this dimmer interacts with a KAKU remote control. Probably the same as any other learnable KAKU dimmer. My supply is 12V 3A stabilized. I tested with a LED strip that usually uses 0.57A at 12V. The LED strip type is a common one, with the usual 3 warm-white LEDs and a resistor, per segment.
At first test, the LEDs were still quite bright at the lowest dimmer setting of 6%.
The dimmer has 'soft start' and 'soft stop'. This is a nice feature for incandescent light bulb dimmers. For LED, it's not needed at all.
Standby current: 4.4mA.
The unit remembers it's learned address on power supply interruptions. It does not remember it's last dimmer % setting and on/off setting, so if Domoticz would send an ON command while the level is 6%, it will light up as 100%. If the power supply is not interrupted, all is fine.
I dusted off my old "Velleman Kit" digital scope. I measured a PWM frequency of 400Hz.
This 400Hz tone can be heard at an annoying level if you connect a 12V computer-fan at 46%, so a low-pass filter is recommended when using this unit to control a fan. You can even hear the tone through a 12V45W incandescent light bulb, if you listen well.
Estimated duty-cycle at lowest 6%-setting is approximately 25%, which is very annoying. Especially because during soft-start and soft-stop, the unit proves to be capable of producing smaller pulses. At 46%-setting, the duty-cycle is approximately 50%.
As said, the unit's specs in Watts are weird. At 24Volt, 75Watt would be 3 amps. At 12V, that would be 6 amps. And a switching device usually has an amp rating. So... Let's open up the unit and see what this is about.
It turns out that the unit's abs case is glued shut. If this unit was rated for mains voltage, that would be good, but in this case, it's just very annoying. It's impossible to open the case without destroying it.
Anyway, the power switch is a P-channel Enhancement Mode MOSFET, like so: http://www.syncpower.com/datasheet/SPP4435W.pdf.
The thing is on a double-sided PCB and there's a bunch of smd resistors, capacitors, 1 unmarked smd chip, 2 barely readable marked smd chips, 2 transistors, a led, a switch, 5 1N4158 diodes, a fat smd glass diode or something and a crystal. The antenna is formed by PCB-tracks on both sides. It has the form of a crude coil. So in this case, the normally round coil's 'surface' is a box of 1mm x 5mm. The core consists of PCB material. Length is approx 25mm, number of 'windings' is 11. At one side, it's connected to the radio circuitry, at the other side, it's not connected.
So, this MOSFET... It's capable of a continuous current of 7amps, according to the datasheet. The gate is properly driven by the circuitry (I measured it). So, when operating at 24V, 168W should be possible. If you're gonna try, check for heat in the area between the terminals. That's roughly where the MOSFET is located in the case. And calculate how much heat dissapation is to be expected and judge by yourself if the case will be able to cope with that.
The price: it costs EUR 23,18 at domotica-shop.nl.
It's not expensive and that MOSFET can switch more than only LEDs. (Don't forget your protection diode when connecting inductive loads, like, relays and motors. And if you're going to dim your relay or motor, expect the 400Hz tone to be heard. Unless properly filtered by an RC filter. (An LC filter can be tricky at pulsed signals. (It will generate volt spikes!)) If you're not going to dim, you will still briefly hear the 400Hz from your relay or motor at start and stop.
This dimmer is to be connected between your fixed-voltage power supply and your led strip. Usually, this kind of dimmers use Pulse Width Modulation (PWM). This one is no exception.
The specs are a bit weird. Usually, such dimmers are rated for max volts and max amps, instead of max watts. The user's manual does not say anything about amps, so this needs further investigation.
The dimmer's form factor is a small white box: 4 x 4.5 x 1.7 centimeter. It has two input terminals: (positive and negative ( + & - )), and two output terminals. The terminals have screws that hold on to the wires. The negative input and output are internally connected and serve as a common ground. There's two small holes: one with a red led and one with a learn button. Learning process is the same as other KAKU switches and dimmers without code wheel selectors.
As usual for KAKU dimmers, we can set the dimmer level in 14 stages. In Domoticz, this is translated to a percentage. Minimum brightness is 6%, one stage under max brightness is 93%. Half bright is 46% or 53%. (I'm using 46%, because at that level the Domoticz slider is approximately in the middle.
Wiring up, learning and configuring in Domoticz is a breeze, if you have a good 433MHz tranceiver connected. I did not test how this dimmer interacts with a KAKU remote control. Probably the same as any other learnable KAKU dimmer. My supply is 12V 3A stabilized. I tested with a LED strip that usually uses 0.57A at 12V. The LED strip type is a common one, with the usual 3 warm-white LEDs and a resistor, per segment.
At first test, the LEDs were still quite bright at the lowest dimmer setting of 6%.
The dimmer has 'soft start' and 'soft stop'. This is a nice feature for incandescent light bulb dimmers. For LED, it's not needed at all.
Standby current: 4.4mA.
The unit remembers it's learned address on power supply interruptions. It does not remember it's last dimmer % setting and on/off setting, so if Domoticz would send an ON command while the level is 6%, it will light up as 100%. If the power supply is not interrupted, all is fine.
I dusted off my old "Velleman Kit" digital scope. I measured a PWM frequency of 400Hz.
This 400Hz tone can be heard at an annoying level if you connect a 12V computer-fan at 46%, so a low-pass filter is recommended when using this unit to control a fan. You can even hear the tone through a 12V45W incandescent light bulb, if you listen well.
Estimated duty-cycle at lowest 6%-setting is approximately 25%, which is very annoying. Especially because during soft-start and soft-stop, the unit proves to be capable of producing smaller pulses. At 46%-setting, the duty-cycle is approximately 50%.
As said, the unit's specs in Watts are weird. At 24Volt, 75Watt would be 3 amps. At 12V, that would be 6 amps. And a switching device usually has an amp rating. So... Let's open up the unit and see what this is about.
It turns out that the unit's abs case is glued shut. If this unit was rated for mains voltage, that would be good, but in this case, it's just very annoying. It's impossible to open the case without destroying it.
Anyway, the power switch is a P-channel Enhancement Mode MOSFET, like so: http://www.syncpower.com/datasheet/SPP4435W.pdf.
The thing is on a double-sided PCB and there's a bunch of smd resistors, capacitors, 1 unmarked smd chip, 2 barely readable marked smd chips, 2 transistors, a led, a switch, 5 1N4158 diodes, a fat smd glass diode or something and a crystal. The antenna is formed by PCB-tracks on both sides. It has the form of a crude coil. So in this case, the normally round coil's 'surface' is a box of 1mm x 5mm. The core consists of PCB material. Length is approx 25mm, number of 'windings' is 11. At one side, it's connected to the radio circuitry, at the other side, it's not connected.
So, this MOSFET... It's capable of a continuous current of 7amps, according to the datasheet. The gate is properly driven by the circuitry (I measured it). So, when operating at 24V, 168W should be possible. If you're gonna try, check for heat in the area between the terminals. That's roughly where the MOSFET is located in the case. And calculate how much heat dissapation is to be expected and judge by yourself if the case will be able to cope with that.
The price: it costs EUR 23,18 at domotica-shop.nl.
It's not expensive and that MOSFET can switch more than only LEDs. (Don't forget your protection diode when connecting inductive loads, like, relays and motors. And if you're going to dim your relay or motor, expect the 400Hz tone to be heard. Unless properly filtered by an RC filter. (An LC filter can be tricky at pulsed signals. (It will generate volt spikes!)) If you're not going to dim, you will still briefly hear the 400Hz from your relay or motor at start and stop.
