Hi everyone,
I am trying to think through a project/design that involves a couple of different aspects. I've been trying to think through it for several days and have read multiple forums, but I keep running into problems, so I just thought asking for advice might be good.
What I'm trying to accomplish:
I'd like to power 2 sets of LEDs from batteries (the project needs to be portable and work anywhere).
My ideas/solutions:
I'm thinking of using 6 volts via 4 AA batteries. (This should be enough V, and last longer than a 9V. It would also allow me to use rechargeable batteries.)
For the first set (14-20 LEDs): I was thinking of controlling them with a 4017 chip running on a 555 signal (say 200Hz). This is to both "dim" the LEDs (though I do worry it will dim them too much, but it should be okay), but mostly so that the battery is powering 2 LEDs at once, not 14-20.
Is there any reason this is a bad idea? Is there a much better solution for what I'm trying to accomplish?
(Looking at the datasheet for the 4017, it seems I should use a transistor to actually drive the 2 LEDs assigned to each 4017 output. The chip cannot put out the 40mA at 6V that I would need, right?)
For the second set (2 sets of 8 light chasing LEDs): I can set up the light chasing with a 555 (with a pot to control the speed) and a 4017. The big issue I have here is the dimming, which I really need on this section. One idea was to setup a PWM with a 555, and then use 2 transistors to make an AND gate (1 input would be from the 4017, the other from my PWM). This really doesn't seem that elegant though (32 transistors).
Another idea was to use a SN74HCT244N with the PWN on the Output enable pin, and using the 4017 to drive the inputs/outputs. This seems much better, but is there any reason this wouldn't work well?
A third idea is to simply use a potentiometer? I may give this a try just to see (if it gives enough dimming range, but it seems easiest by far). The grounds of the LEDs could all be tied together and go through the pot. Is there a reason to avoid this solution (burning of battery power as heat, for example). Or is this the way to go, instead of trying to power a bunch of ICs from my already taxed batteries?
The big picture:
In case this is helpful, here's the larger scope of what I'm trying to do: I am making a portable sign for a friend. I am carving out wooden letters and then want to light them from above and below the letters (this is the first set of LEDs). The sign will have 2 Os, and I will install LEDs into those letters and want to do the whole light chasing thing. I'm just saying this in case there's like a way better way to approach the whole thing that I've missed here. (The sign will mostly be used in dark(ish) places, where the LEDs don't need to be that bright -- and too bright would be bad.)
PS:
What I originally wanted to was put LEDs into each letter, but this would have been like 70 LEDs total and I decided that was just too much to try to power with batteries (even with switching action and whatnot). However, maybe someone does have advice on how to do this. If so, I'd love to hear it.
(Could I maybe setup a 4017 for each of the 7 letters. 5 of them to just cycle through LEDs at ~200Hz, and 2 to cycle slowly? This would still leave the batteries powering 7 or so LEDs at a time as well as two 555 and like nine 4017s (a couple of letters would be more than 10 LEDs. I am trying to learn, but at this point, I have no idea if that's a reasonable thing to try, or totally bonkers.)
Thanks so much! Sorry for the long post; I wanted to give all the information that might be relevant. Thanks again!
I am trying to think through a project/design that involves a couple of different aspects. I've been trying to think through it for several days and have read multiple forums, but I keep running into problems, so I just thought asking for advice might be good.
What I'm trying to accomplish:
I'd like to power 2 sets of LEDs from batteries (the project needs to be portable and work anywhere).
- 1 set would need to appear to be on all the time, and it would be nice if it was dimmable. This would be 14-20 LEDs.
- 1 set would be "light chasing", so the LEDs would turn on, one after the other in a circle. (This would be 2 subsets of 8 LEDs, 16 total.) This would need to be dimmable.
My ideas/solutions:
I'm thinking of using 6 volts via 4 AA batteries. (This should be enough V, and last longer than a 9V. It would also allow me to use rechargeable batteries.)
For the first set (14-20 LEDs): I was thinking of controlling them with a 4017 chip running on a 555 signal (say 200Hz). This is to both "dim" the LEDs (though I do worry it will dim them too much, but it should be okay), but mostly so that the battery is powering 2 LEDs at once, not 14-20.
Is there any reason this is a bad idea? Is there a much better solution for what I'm trying to accomplish?
(Looking at the datasheet for the 4017, it seems I should use a transistor to actually drive the 2 LEDs assigned to each 4017 output. The chip cannot put out the 40mA at 6V that I would need, right?)
For the second set (2 sets of 8 light chasing LEDs): I can set up the light chasing with a 555 (with a pot to control the speed) and a 4017. The big issue I have here is the dimming, which I really need on this section. One idea was to setup a PWM with a 555, and then use 2 transistors to make an AND gate (1 input would be from the 4017, the other from my PWM). This really doesn't seem that elegant though (32 transistors).
Another idea was to use a SN74HCT244N with the PWN on the Output enable pin, and using the 4017 to drive the inputs/outputs. This seems much better, but is there any reason this wouldn't work well?
A third idea is to simply use a potentiometer? I may give this a try just to see (if it gives enough dimming range, but it seems easiest by far). The grounds of the LEDs could all be tied together and go through the pot. Is there a reason to avoid this solution (burning of battery power as heat, for example). Or is this the way to go, instead of trying to power a bunch of ICs from my already taxed batteries?
The big picture:
In case this is helpful, here's the larger scope of what I'm trying to do: I am making a portable sign for a friend. I am carving out wooden letters and then want to light them from above and below the letters (this is the first set of LEDs). The sign will have 2 Os, and I will install LEDs into those letters and want to do the whole light chasing thing. I'm just saying this in case there's like a way better way to approach the whole thing that I've missed here. (The sign will mostly be used in dark(ish) places, where the LEDs don't need to be that bright -- and too bright would be bad.)
PS:
What I originally wanted to was put LEDs into each letter, but this would have been like 70 LEDs total and I decided that was just too much to try to power with batteries (even with switching action and whatnot). However, maybe someone does have advice on how to do this. If so, I'd love to hear it.
(Could I maybe setup a 4017 for each of the 7 letters. 5 of them to just cycle through LEDs at ~200Hz, and 2 to cycle slowly? This would still leave the batteries powering 7 or so LEDs at a time as well as two 555 and like nine 4017s (a couple of letters would be more than 10 LEDs. I am trying to learn, but at this point, I have no idea if that's a reasonable thing to try, or totally bonkers.)
Thanks so much! Sorry for the long post; I wanted to give all the information that might be relevant. Thanks again!