Also look this, I am turning leds off and on again. Slow response and colours changing while doing:
NEWBIE HERE, please help
- Wim
- Erledigt
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If you can lower the led voltage from 5 to 4.5v this will have a similar effect to using a level shifter while you wait.With a diode 5W (should lower 0,65V)? I'm sorry I'm not that technical, just found these googling. Good enough or are there better options?
Wim
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The best level shifter is a 74HCT chip - I didn't get great success with this mosfet levelmshifters.
The 74HCT125 is popular.
Don't buy a diode - if only use that as a test if you had some at hand
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The best level shifter is a 74HCT chip - I didn't get great success with this mosfet levelmshifters.
The 74HCT125 is popular.
Don't buy a diode - if only use that as a test if you had some at hand
There seem to be a lot different kinds to choose:
http://nl.farnell.com/search?st=74hct125Or are they all okay? Just different connections?
Wim
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From https://hyperion-project.org/t…lect.279/page-2#post-2668 :
I used the 74AHCT125D
It's SMD, my local shop only had those in SMD.
As penfold said though its important to use the T variant, so it will have TTO compatible threshold voltages.
The other conditions the chip needs to fulfill are 5V VCC so it can act as a level shifter, taking the 3.3V logic signals from the RaspberryPi and outputting 5V for the LED strip.
I couldn't find SMD nor T variants of the 74HCT125.Hi,
Now a Level shifter (or Bus buffer as I see the data sheets call it) takes a lower voltage data signal and boost's it to a 5v signal. So the LED's have a strong signal and less likely to glitch from data signal interference. I use SN74AHCT125N shifter / buffer's. Some diagrams in a previous post here ( https://hyperion-project.org/t…y-question.935/#post-6977 )
Overlooked the 'N' in your post. Thought I found it, searched for 74HCT125N, not available anymore.
Looked again, you wrote SN74AHCT125N, not 74HCT125N. So this one must be it:
http://nl.farnell.com/texas-in…nt14_Netherlands%2FsearchOrdering one now. Hope it's the wright one.
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I can get the
SN74HCT125N
instead of the
SN74AHCT125N
Would that be okay too? -
I just got one SN74HCT125N.
But I can't understand the wiring now (only pins 7 and 14 of the chip ;)):
http://www.ti.com/lit/ds/symlink/sn74hct125.pdf -
yes. it is ok
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yes. it is ok
Thanks, but now the wiring. -
5V led: 14
GND led: 1/4/7/10/13. All or just one? Which?
DIN led: 3/6/8/11. All or just one? Which?
Which to pi?
Or is 1-7 the pi side, 8-14 the led side?
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OE: GND
A: in
Y: out
So I guess it's a 4- channel type.Perhaps:
7 GND led
14 5V led1 GND pi
2 MOSI pi
3 DIN ledBut I think the chip needs voltage of the pi (3,3) somewhere too.
???
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OE=output enabled, would that be the 3,3V of the pi?
1=3,3V pi
2=MOSI pi
3=DIN led
14=5V led
7=GND ledBut then, where's the GND of the pi?
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I guess GND of pi on 7 too?
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No, I believe I have to connect:
1OE and 2OE and 3OE and 4OE to GND led(+pi?)
GND to GND led(+pi?)
1A (or 2A or 3A or 4A) to MOSI pi
1Y (or 2Y or 3Y or 4Y) to DIN ledI guess unlike level-shifter used here:
https://hyperion-project.org/wiki/using-level-shifterThe 3,3V of the pi doesn't need connected?
Questions: is the above correct?
Do I need to connect ALL of the OE's to GND?
Do I need to connect GND of the pi to GND? Probably not? -
Ground must be connected between rpi, level shifter and led strip.
All unused inputs on the chip should be grounded
Chip needs 5v - use the 5v pin on the Pi or from the led strip but not both
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Ground must be connected between rpi, level shifter and led strip.
All unused inputs on the chip should be grounded
Chip needs 5v - use the 5v pin on the Pi or from the led strip but not both
Thanks. Will report back asap. -
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This is what I built, albeit for apa102s but it might help...
https://hyperion-project.org/t…th-apa102s.822/#post-6165
Lives in a tictac 100 box behind the telly.
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And......... IT WORKS. YEAAAAAAAHHHHHHHHHH. Thanks everybody for the help and support.
I don't have the capacitor yet, going to buy one soon. 1000uF between 5V and GND feeding the chip.
I'm also considering now to drop the separate power supplies. I can connect the 5V of the leds directly to pins 2 or 4 of the pi.Now I am going to calibrate colors following this guide:
https://hyperion-project.org/wiki/Color-CalibrationAnd then I'm going to make a decent frame to mount at the back of the tv.
Is there a description on the wiki or forum what is advised regarding the distance of the leds from the edge of the tv (parallel to the tv)?
I'm mounting them 180 degrees (on the back of) the tv, facing them to the wall.Wim
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Yay !
Personally I don't like powering my Pi via gpio pins or the same PSU as the leds.
You may get voltage fluctuations depending on how well regulated the PSU is when the leds go from very dark to very bright.
If you are messing with the leds and screw something up, your Pi crashes and might corrupt the card
If you accidentally put power into the wrong gpio, bye bye Pi.
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