On Friday, August 10, 2012 2:56:15 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote:> > >PS: Have you seen the MAX7219 LED driver chip? > >It's similar to the TLC5916 but has built in > >multiplexing for 8 rows of LEDs. > > But it's Maxim. Good luck actually getting them.Go to eBay and type "MAX7219". There's no shortage of them on there...
How to power my circuit.
Started by ●August 7, 2012
Reply by ●August 10, 20122012-08-10
Reply by ●August 10, 20122012-08-10
On Fri, 10 Aug 2012 06:34:09 -0700 (PDT), fungus <tooby@artlum.com> wrote:>On Friday, August 10, 2012 2:56:15 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote: >> >> >PS: Have you seen the MAX7219 LED driver chip? >> >It's similar to the TLC5916 but has built in >> >multiplexing for 8 rows of LEDs. >> >> But it's Maxim. Good luck actually getting them. > >Go to eBay and type "MAX7219". > >There's no shortage of them on there...This week.
Reply by ●August 10, 20122012-08-10
"krw@att.bizzzzzzzzzzzz" wrote:> > On Fri, 10 Aug 2012 06:34:09 -0700 (PDT), fungus <tooby@artlum.com> wrote: > > >On Friday, August 10, 2012 2:56:15 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote: > >> > >> >PS: Have you seen the MAX7219 LED driver chip? > >> >It's similar to the TLC5916 but has built in > >> >multiplexing for 8 rows of LEDs. > >> > >> But it's Maxim. Good luck actually getting them. > > > >Go to eBay and type "MAX7219". > > > >There's no shortage of them on there... > > This week.No, there has been new listings there for over six months.
Reply by ●August 10, 20122012-08-10
On Friday, August 10, 2012 2:54:55 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote:> > >eg. In the context of this project you'll > >need 4xAA for it to work. > > .6V overhead is all that's needed. >ie. You need 4.2 volts - 3xAA isn't enough> >Even 4xAA is marginal for a 3.6V LED. > > Nonsense. It works. BJT + FET >With a 0.6V overhead and a 3.6V LED it'll work down to 4.2V before the current drops. That's not *quite* dead, ie. "marginal".> >ie. In most practical contexts the extra > >efficiency probably cancels out. > > Simply wrong, as shown.How? a) You have to stick an extra battery in. b) Your BJT+MOSFET (or whatever) is acting exactly like a ballast resistor. It will use the same power. To increase the efficiency you'd have to use a PWM circuit which produces an *average* current without consuming much power itself.
Reply by ●August 10, 20122012-08-10
On Fri, 10 Aug 2012 07:09:44 -0700 (PDT), fungus <tooby@artlum.com> wrote:>On Friday, August 10, 2012 2:54:55 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote: >> >> >eg. In the context of this project you'll >> >need 4xAA for it to work. >> >> .6V overhead is all that's needed. >> > >ie. You need 4.2 volts - 3xAA isn't enoughYou don't need 3.6V unless you want to put your eye out.>> >Even 4xAA is marginal for a 3.6V LED. >> >> Nonsense. It works. BJT + FET >> > >With a 0.6V overhead and a 3.6V >LED it'll work down to 4.2V before >the current drops. > >That's not *quite* dead, ie. "marginal".See above.>> >ie. In most practical contexts the extra >> >efficiency probably cancels out. >> >> Simply wrong, as shown. > >How?You CANNOT gain efficiency by boosting the voltage and then pissing it away in a ballast resistor. A current source is simply a variable resistor.>a) You have to stick an extra battery in.Wrong.>b) Your BJT+MOSFET (or whatever) is acting >exactly like a ballast resistor. It will >use the same power.No, because it's *NOT* boosted to your 5V.>To increase the efficiency you'd have to >use a PWM circuit which produces an *average* >current without consuming much power itself.No.
Reply by ●August 10, 20122012-08-10
On Friday, August 10, 2012 6:03:37 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote:> > >ie. You need 4.2 volts - 3xAA isn't enough > > You don't need 3.6V unless you want to put your eye out >Ahhhh, your argument is based on not running the 3.6V LED at 3.6V. Got it. In that case I'm going to run mine at 2.5V. I can connect two of them in series and get over 90% efficiency. Let's see if your current source can beat that!> You CANNOT gain efficiency by boosting the > voltage and then pissing it away in > a ballast resistor.I'm not saying you can. I'm saying that with an extra battery your circuit will have a fairly similar efficiency to my booster-board circuit. If you're not adding a battery then you obviously win unless I can find a 3.6V booster.> A current source is simply a variable resistor. >No argument there.
Reply by ●August 10, 20122012-08-10
On Fri, 10 Aug 2012 09:49:38 -0700 (PDT), fungus <tooby@artlum.com> wrote:>On Friday, August 10, 2012 6:03:37 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote: >> >> >ie. You need 4.2 volts - 3xAA isn't enough >> >> You don't need 3.6V unless you want to put your eye out >> > >Ahhhh, your argument is based on not running >the 3.6V LED at 3.6V. Got it.A 3.6V LED is only 3.6V at its rated current. Unless you're lighting a room, it's *not* needed. It'll be quite visible at 1/4 (or 1/10) of its rated current. At 1/4, we found that blues were quite visible in full sunlight. Running them "hotter" is nuts.>In that case I'm going to run mine at 2.5V. >I can connect two of them in series and get >over 90% efficiency. Let's see if your current >source can beat that!We now know you're an idiot.>> You CANNOT gain efficiency by boosting the >> voltage and then pissing it away in >> a ballast resistor. > >I'm not saying you can. I'm saying that >with an extra battery your circuit will >have a fairly similar efficiency to my >booster-board circuit.Utter nonsense.>If you're not adding a battery then you >obviously win unless I can find a 3.6V >booster.You're still paying 11% for the boost.>> A current source is simply a variable resistor. >> > >No argument there.
Reply by ●August 10, 20122012-08-10
On Friday, August 10, 2012 9:06:13 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote:> > A 3.6V LED is only 3.6V at its rated current. > Unless you're lighting a room, it's *not* needed.Says who? Not all LED applications are "can you see the LED?"> We now know you're an idiot. >Me? You're the one picking a particular voltage and arbitrary LED brightness that just happens to support your claim. If we're allowed to pick and choose then I'll get an adjustable boost board, eg: http://www.ebay.com/itm/130736597148 I can use that to one with 2xAA batteries. It uses PWM switching to do its job, I bet it's more efficient for lighting an LED than 3xAA plus a current source that's guaranteed to eat 0.6V.
Reply by ●August 10, 20122012-08-10
On 8/10/12 3:13 AM, fungus wrote:> On Friday, August 10, 2012 2:01:47 AM UTC+2, Daniel Pitts wrote: >> >> Actually, I'm planning on using the TLC5916 from TI, which is a >> >> constant-current sink 8bit shift register, for exactly this purpose. >> >> That way brightness will be consistent. > > PS: Have you seen the MAX7219 LED driver chip? > It's similar to the TLC5916 but has built in > multiplexing for 8 rows of LEDs. >I've already got my TL5916 (I'm using a 74HC238 to multiplex). Also, if I recall, the MAX7219 was much more expensive for what I needed. I got my TL5916 for 88 cents, and the 74HC238 for 25 cents. Where the MAX7219 is over $10 from the same supplier ($13 if I wanted DIPS, which I do for now). So to power 192 LEDs (8x8xRGB) I could spend spend over $30 using MAX7219, or I could spend just 3*.88+.25=$2.89. I think a 90% cheaper solution is the better solution, especially for a hobby project.
Reply by ●August 10, 20122012-08-10
On Fri, 10 Aug 2012 13:19:53 -0700 (PDT), fungus <tooby@artlum.com> wrote:>On Friday, August 10, 2012 9:06:13 PM UTC+2, k...@att.bizzzzzzzzzzzz wrote: >> >> A 3.6V LED is only 3.6V at its rated current. >> Unless you're lighting a room, it's *not* needed. > >Says who? Not all LED applications are "can >you see the LED?"You don't want to see the LED? Read the fucking thread before you make more of an ass of yourself.>> We now know you're an idiot. >> > >Me? You're the one picking a particular voltage >and arbitrary LED brightness that just happens >to support your claim.You really are trying to be right at all costs, even by being wrong. Are you really on Obama's campaign team?>If we're allowed to pick and choose then I'll >get an adjustable boost board, eg:Of course you would. You've already demonstrated that you're clueless.>http://www.ebay.com/itm/130736597148 > >I can use that to one with 2xAA batteries. >It uses PWM switching to do its job, I bet >it's more efficient for lighting an LED than >3xAA plus a current source that's guaranteed >to eat 0.6V.If you're going to all that trouble, just use a damned wall wart and be done with it.
