[HELP] 93 SMD LED GU10 230V circuit/driver?

[whc]

Hi, I bought some cheap 93 SMD 1210 LED GU10 bulps, that is rated to 380 Lumens, but IRL they are more cloose to 120 Lumens. It should be possible somehow to boost the circuit/driver to produce 3x the amount of light right?

Tried some different resistors, boosting the output slightly, but no where near 3x the output/the output seller claimed.

Well, can someone here with the expertise give me some pointers to how this is possible, pretty simple driver/circuit, must be possible to do this some how.

Download full size images here: http://gallery.wcw.dk/#81.0

 

[SemiMan]

You made the mistake of assuming the resistor is what is limiting current but it is not, it is the capacitor. The resistor is 510K. However, at 60Hz, that capacitor is 2.5K. Guessing if you change this, you can kiss the life of those LEDs goodbye but if you do not find it useful now, then not much harm ... as long as it does not start on fire.

Was this a purchased product assembled? In normal operation is there anything to prevent some one from touching the LEDS? If not that is pretty scary.

Semiman

 

[whc]

You made the mistake of assuming the resistor is what is limiting current but it is not, it is the capacitor. The resistor is 510K. However, at 60Hz, that capacitor is 2.5K. Guessing if you change this, you can kiss the life of those LEDs goodbye but if you do not find it useful now, then not much harm ... as long as it does not start on fire.

Was this a purchased product assembled? In normal operation is there anything to prevent some one from touching the LEDS? If not that is pretty scary.

Semiman

Thanks, if I want 3x the output what capacitor would you recommend.

Got some with 48 SMD LED of same type, they got doubble the brightness, so would not expect them to burn off if not overloaded, or what?

They came assembled, yes the LED's is not protected, use them in a lamp with four bulps in the sealing. It is these: http://cgi.ebay.com/GU10-93-SMD1210...691?pt=LH_DefaultDomain_0&hash=item2a10ee9943

 

[Steve K]

It looks like the cap is 1uF, 400v. Adding a second cap in parallel with the original would double the current, and presumably double the LED brightness. Digi-key sells a part that appears to be suitable for $1.
Digi-key sells a 2uF version for about $3. This may be the preferred option, since there may not be room for two of those 1uF caps in that light.

This will double the heat generated in the LEDs, so keep an eye on the temperature.

regards,
Steve K.

 

[whc]

It looks like the cap is 1uF, 400v. Adding a second cap in parallel with the original would double the current, and presumably double the LED brightness. Digi-key sells a part that appears to be suitable for $1.
Digi-key sells a 2uF version for about $3. This may be the preferred option, since there may not be room for two of those 1uF caps in that light.

This will double the heat generated in the LEDs, so keep an eye on the temperature.

regards,
Steve K.

Ok, thanks, am going to try this, sure it would be the solution, see here where I have marked the lanes on the print board:

 

[arek98]

I believe capacitors Steve K linked are DC rated. You need AC rated one and since you are in Europe at least 250V.
Here is 2uF for example.

Circuit you see is basically this without R2 and bridge in single package. C1 smooths output, I guess in your case it is only 10uF to keep on delay short (bigger would remove ripples better but you would see delay when turning light).

 

[Steve K]

When I was looking up the cap on the Digi-key site, I saw that there were AC ratings and DC ratings, which was new to me. Are the AC ratings just intended to show that the cap is rated to handle more ripple current? I may have to pull up the cap datasheet and see what it can tell me (note to the casual reader... it's always good to review the datasheet and any application info to see what the parts are rated for, how to interpret the ratings, etc.).

thanks,
Steve K.

 

[whc]

So what exactly do I need to do to boost the overall output of the leds?

 

[arek98]

Ok, I'm not an expert but I will try to gather some bits. Maybe someone educated will chime in.

AC capacitors are usually X or Y rated. I believe they are made to work at 50/60Hz frequency and survive voltage spikes (I think I read somewhere that this constant wave stretches capacitor internally).

Also AC is sinus wave. Assuming 250V RMS voltage value we get 707V maximum voltage (250 * 2 * sqrt(2)). Capacitor does not care about RMS, it needs to survive max voltage.

So what exactly do I need to do to boost the overall output of the leds?

You need bigger capacitor. 2uF instead of 1uF that you have currently (big red 105J means 1000000pF=1uF 5% tolerance). It will double output current. You can connect second 1uF in parallel or replace original with 2uF.

 

[Steve K]

the Digikey page has links to Panasonic's web site (it's a Panasonic cap that I recommended). The Panasonic site does have a paper that discusses the AC capability of their DC rated film caps. It looks like their 400vdc cap is good for a 230vac rms AC system, so you wouldn't want to use it with your 230vac system.... except that you won't actually have 230vac across the cap. Some portion of the voltage is across the LEDs, so the 400vdc caps might actually be okay. You could measure the voltage across your LEDs now, knowing that they will have a slightly higher voltage across them when you increase the current.

Panasonic has a paper called "caution about safety in use". Sounds like it's worth reviewing. For instance, Panasonic recommends derating caps by 0.75. So for a 230vac application, use a cap rated for 300vac or more. Page 4 discusses allowable currents. For 1uF caps, it talks about pulse currents over 1A, so an application like this is likely safe. As a general rule, even when you think you've done things right, it wouldn't hurt to check the temperature after running it for 10 or 20 minutes (as you sit next to the power switch). After turning it off, if the cap feels noticeably warm, it's probably a problem.

The characteristics for this particular family of film caps is here. It shows a 1uF film cap being rated for over 1 amp, so the 20mA or 40mA that you would put through those LEDs is fine. ...and that's for the 400vdc part.

I'd go for something rated for 300vac at a minimum, and then check the temperature when you check it out.

a note to arek98: the cap will only see the rms voltage times sqrt(2), although it will see it in both the positive and negative direction.

what's available from Digi-key???
Here's a cap from Epcos... 2uF, 300vac. Wouldn't hurt to check the datasheet before ordering.

There's a Panasonic, 630vdc cap, 2.2uF for about $3. Not sure if it's too big or not (physically). I'd recommend checking to see if this family of caps is the same as the data I was referencing earlier.

There are some Panasonic caps with a 300vac rating, but the largest that they show is a 1uF part. You'd need to put this in parallel with the existing cap. Only $2, so that's okay.

Anyway... now you have a feel for the level of detail work that is needed to produce a well designed product!

regards,
Steve K.

 

[SemiMan]

No need for an AC rated capacitor in this application since the voltage is unipolar. There is a full-wave bridge rectifier on that circuit. Either way this is a bipolar cap so would work for AC.

Should derate for voltage since capacitance can change w.r.t. voltage though poly caps are pretty good for this. Realistically, the only time that CAP is going to see anything near line voltage peak is when that electrolytic is fully discharged and this thing first turns on. After that is going to see a lot less.

Note that the electrolytic is only rated 200V. That leads me to believe this is 48 LEDs in series at about 3.3-3.5V per LED or 170V max. No doubt tons of ripple on this thing. Likely no more than 150-180V across the "resistor" cap.

Increasing the 1uF is going to increase the ripple on the LEDs output. Not sure how much.

No heat transfer from front to back of board.. yup these LEDs are going to cook.

Semiman