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You CAN dim LEDs without power cycling. It just takes a little math to figure the current limiting resistors.

draehn wrote:You CAN dim LEDs without power cycling. It just takes a little math to figure the current limiting resistors.

True. The light from a LED is roughly proportional to the current. All the power cycling does is create a lower average current.
Personally, I hate that, unless the frequency is very high. Apparently I have eyes that are very sensitive to flicker.

There a number of online calculators to help flesh out the current limiting resistor for a string of LEDs. Once you know the value of the resistor, you can substitute a potentiometer for 2/3 of the value and a resistor for the last 1/3. That way you can go from full brightness down to just a little bit, without the LEDs going out at the bottom of the scale.

I didn't check this thread over the last 36 hours and in that time, I have bought a 1KΩ linear variable resistor to see if I can get some dimming action. The LED strip is laid out in groups of 3 LEDs, each group having a 151Ω resistor leading off from the +12V line, through 3 LEDs and then to ground. I haven't worked out whether to use all 3 pins of the vari resistor, so that you take the voltage to be used from the third pin and have the 1st connected to 12V and the third to ground. The other way (that I think I will use) is to use the vari resistor in series and only use 2 pins... one for in and one for out (all on the 12V rail). This way I can just adjust the resistance, which should drop the voltage.
I will test tonight, but is either method acceptable if I get it working? (i.e. I won't cause PSU to blow up or anything like that!)

Thanks

Just use two of the leads on the variable resistor. Center and one of the others. Nothing should blow up .

draehn wrote:Just use two of the leads on the variable resistor. Center and one of the others. Nothing should blow up .

Well, not sure about that. A regular potentiometer has a power rating AND a max current rating. I've smoked a few when I haven't paid attention, and been close to zero resistance on the pot, thus getting too much current.

Well they are only 99p each, so no biggie if I smoke it! I don't think the PSU gives out massive amps... it's for an hard drive caddy, so it'll be ok.

I have had to start again after realizing that my LEDs were pointed too much downward after I used the 45 degree router bit. I remade the strip of wood with a 15 degree slope (using the circular saw) and it is much brighter across the whole of the mixer/CDJs and reflects less also. I still haven't worked out why I used the router bit instead of the circular saw as I knew I only wanted a shallow slope

draehn wrote:Just use two of the leads on the variable resistor. Center and one of the others. Nothing should blow up .

This is how I have ended up doing it. I originally used a linear resistor, but reducing the brightness of the LEDs (i.e. increasing the resistance of the pot) caused too much of a jump in the brightness. I therefore bought a logarithmic resistor and have used that instead. The problem, whilst still there, is much reduced and it's much easier to now get the desired brightness Annoyingly the small Δ is at the start of the resistor, so I have had to wire it so that you turn it anticlockwise to increase brightness and clockwise to decrease... a bit wrong, but it's not like I am going to be constantly fiddling with it.
This is what the pot looks like all glued in and ready to rock!

Note how I doubled up using the lid hinges to hold my laptop tray Well, I thought it was pretty clever

And here's what that little pot does:


Sorry this isn't really BFM stuff, but it's all rig related, so thought I'd put it here. The reason why there are no pics of the T30 is that nothing has changed since the last pics. I am waiting for my local yard to get in my beloved 1/2" BB AND also waiting for an order of PL to turn up. I am stymied until these arrive, hence why I have been fiddling with other bits. The woodyard should have the wood in tomorrow

Hey that looks sweet, well done.

Looks good brother!

Don't worry about your wood and PL not having arrived. I need all the advantage i can get, ...oops, I'm not supposed to say that. More power to you escape! The thing that occured to me was that if you finished a work contract and are brass flint, what about living/subsistence costs, etc.? Apologies, I know its personal, I just wouldn't want to hear you're living in the woods or anything like that, even though that would be quite exiting on one level.

Weekend warrior has a new meaning for me, associated with being when i can build. I could do with some of that garden leave.

No... I'm good on the subsistence thing... Living with parents which is both a positive and negative.

Positives
Cheap living
Big garage to build big speakers in

Negatives
Living with parents, having them comment on everything I do!

I have pretty well much spent all my spending money this month, but as I contract, I still have another payday to come. I almost have all the bits to 'complete' my rig (until I decide to build more that is ), so I will be spending very little else this month whilst I'm in the garage. It's because I live with the parents at the moment that I decided to take on this build... I couldn't have contemplated it if I was in a one bedroom flat. It can be difficult living with parents now and then, but I don't really see that because I'm an optimist... I see a garage going spare and a need to fill it

P.S. love you m+d

I spent two weeks of holiday this year on building speakers. I found it actually works out cheaper for me to be busy in the garage than to be away somewhere spunking coin left, right and centre.

Also how come there's no such thing as a house with more garage space than rooms? All I want is a living room, a bedroom and a bathroom then loads of space to get stuff built. Oh and room for my own squat rack because I hate people at the gym.

88h88 wrote:I spent two weeks of holiday this year on building speakers. I found it actually works out cheaper for me to be busy in the garage than to be away somewhere spunking coin left, right and centre.

Agreed... After my initial splurge this month, I will be barely spending a penny. Hoping I have remembered everything (bet I haven't though )

88 wrote:Also how come there's no such thing as a house with more garage space than rooms? All I want is a living room, a bedroom and a bathroom then loads of space to get stuff built

There's never enough space!! I have a double garage at my disposal and I'm still having problems getting around because of all the various bits of speaker littered around!!!

And still no bb at the woodyard PL has turned up though

escapemcp wrote:Agreed... After my initial splurge this month, I will be barely spending a penny. Hoping I have remembered everything (bet I haven't though )

I think all I need to finish my OT12s this week is corners which I ordered this morning... Oh and screws for them. I have all my crossovers bits and the internal foam, mesh for the grille and indeed acoustically clear foam for behind it. Hmm. Something will go awry, I know it.

88h88 wrote:Something will go awry, I know it.

Yup, but at least you are aware of your impending cock-up, even if you don't yet know what it is!!

I need some help tonight if possible. My local woodyard are saying that the BB they have ordered may still take a week to arrive. I really need to crack on with my build as I have a week or 2 off between jobs... losing these due to lack of materials would be a real PITA.

After reading another thread on here entitled Weight of a T39 loaded with a BP-102????? at http://billfitzmaurice.info/forum/viewt ... =1&t=20571, I realized that you guys in the US sometimes use Auraco, which is pine ply. This made me realize that I could switch to using this instead of BB. Apparently it is much lighter also, which can only be a plus (I think).

I had a look on my supplier's webpage and found both Pine and Spruce 12mm ply. The page is here: http://www.meyertimber.com/default.aspx ... atid=14761

Can someone please let me know if the wood listed would be suitable (I know about the thin veneer thing) and if there would be any positives or negatives in using either pine OR spruce. A quick answer on this would be VERY MUCH APPRECIATED, as I'd like to go and pick up the wood tomorrow (in 12 hours), so that I can use my time off to build speakers, rather than dreaming of building them!!

Thanks in advance for any input. Hoping for a positive answer, but please don't pull any punches if it isn't quite as good for whatever reason - if you can just let me know the facts so that I can make a (more) informed decision, it would be massively appreciated.