Replacement LED driver compatibility?

1 Sep 2015
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United Kingdom
We've got some trailing edge LED dimmers fitted at home, however they're not ones where the module can be replaced and we'd rather not replace them as they weren't particularly cheap.

We bought a ceiling light that said it was dimmable, however it turns out that its powered by an LED driver that is a actually a 3 step dimmer which isn't compatible.

Does anyone know what a suitable dimmable (trailing edge) driver would for this light?

Current specs say:
PRI: 220-240VAC 50/60Hz 0.14a
SEC: Constant Current DC26-38.5v 650mA Max 55vDC
Load: 25W Max

I found this one which I think is suitable, but I'm not 100% sure:
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Constant Current is the key, so 650 mA LED is not going to like 900 mA.

Getting LED lamps to work seems to be a problem, the LED can have thermal run away, so some thing is required to limit the current, be it inside the bulb or outside, but although the LED is DC the perceived brightness can be increased by pulsing the supply, so really looking at a RMS current valve not peak.

So three main methods of control are, the resistor, not good as resistor gets hot, but 3 LED's at approx 3 volt and a resistor at 3 volt on a 12 volt supply is common. Next is the capacitor, it has to be AC and at a set frequency, but it is the standard method with many 230 volt lights, and the last two names for basic same idea, switch mode power supply (SMPS), or pulse width modulated (PWM) power supply, so what it does in the main is turn the AC to DC, charge a capacitor, turn it back to AC at a high frequency so a very small transformer can be used, then back to DC, and either the current or voltage is monitored, and the info sent to the DC to AC converter, and it alters the on/off (mark/space) ratio to adjust the output.

In some cases the PWM is all built into one chip, so cheap they can be built into the bulb.

Also we have a problem because using a capacitor it can store the small amount of energy until voltage is high enough then discharge through the LED, so switched off with an electronic switch the LED flashes each time it builds up enough voltage, so a leak resistor is included to stop it. But the big problem is pulses DC unless smoothed causes the LED to flash although very fast, which can upset some photo sensitive people and machines (cameras).

This pulsing can also effect the next device, so a SMPS/PWM feeding a SMPS/PWM device can cause some very odd results. My electronic light switches (Energenie MiHome) needed a load capacitor across light bulbs to work. Even then it shimmered, so had to change bulb, G9-comp.jpg the large bulb has a smoothing capacitor in it and works OK, the small one also G9 has a shimmer. But there is nothing on the packaging to tell you why one works and other does not. In fact the large bulb should not be sold in UK as no lumen or watts marked on the bulb, but it works, and the small one that does comply does not.

The main problem is it is all trial and error, I have a draw full of new bulbs, that did not work, there is nothing to say which will and which will not work, so bedroom I NEED a remote control, so still use smart light switches, all other rooms removed, I still use plug in devices with table lamps, standard lamps and other mood lighting, but plug in, so can also unplug when it goes wrong.

Be it the AC, battery charger, outside light, display cabin lighting, kitchen floor lighting, or fan, I use plug in devices now, zigbee seems to date to work well, some times all built into the bulb, wife's bedroom two zigbee bulbs both work from same zigbee remote give mood lighting and lower light level to main lights. Two devices off same remote, however using phone one is colour changing can even have a blue light.

I was dead against using bulbs with built in zigbee control, I felt it was simply too expensive to replace if they failed, but compared with hassle of swapping light switches and sockets after they fail, it seems in hind sight better to use the bulbs, must admit with 8 bulbs in main chandelier, not so keen to use smart bulbs, but it is better than having to swap a smart light switch for a standard one when it fails. At moment I am using the old system, I tell the wife to switch on the lights, must get some return for money paid for marriage licence!
Cheers for the reply! I believe that the driver I linked is variable, so the DIP switch can be changed to allow for a 650mA output at 9-42V.

Ideally what I'd like to be doing is similar to you, use a Zigbee rotary dimmer to control the LED driver. The LEDs themselves aren't actually bulbs, they're just LED tape. I've had a look and it seems they're just soldered to wire which goes straight to the driver, so I doubt there's anything fancy about them.

As a starting point, would you say that the driver spec itself is fine as a match for the existing stepped driver? If it works, great and it'll be safe, if it doesn't guess I'll try another
I bought Lidi LED tape with their driver and a Zigbee hub, out of interest I measured the power used, 3 watt to 22 watt, I think it unlikely you will find a PWM power supply with that range unless bought with the LED strip.
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... I was dead against using bulbs with built in zigbee control, I felt it was simply too expensive to replace if they failed, but compared with hassle of swapping light switches and sockets after they fail, it seems in hind sight better to use the bulbs....
how often have you had to replace 'failed light switches and sockets', particularly the former?

As a matter of interest, roughly how much do these "bulbs with built in zigbee control" actually cost?

Kind Regards, John
Fitted 5 smart light switches, now down to 2, only been in house 2½ years, had one socket go faulty.

The first Zigbee bulb was £3 old Lidi stock, new stock is £7 each, the problem is three bases, GU10, E14, and E27, and at 5 bulbs in a chandelier gets expensive, but one bulb not worth fitting a smart switch as they don't last any longer than bulbs.
Fitted 5 smart light switches, now down to 2, only been in house 2½ years, had one socket go faulty.
I knew there was some reason why I have kept well away from all these new-fangled replacements for tried and tested and very lonmg-lasting things :)

Kind Regards, John
Yes very disappointed, the first socket, light switch and TRV heads worked well, so brought them with me when we moved, but Home Base was selling off a load cheap and we got extras at that time when cheap, that is when the problems started, I think they were interfering with each other.

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