HeyAwesomePeople:
It describes that a capacitor is used to filter out any(essentially) unwanted voltage or AC ripples. Could this mean that I could strictly limit the voltage going to the chip to 5volts using a capacitor. If so, how so?
No. A capacitor works with a voltage regulator, it cannot replace it.
A capacitor stores energy and releases it over time. It basically smooths out variations in a voltage by raising the average voltage to near the peak voltage. Any voltage regulator has some variation in its output, either because it is reacting to changes in the load, or because of the way it works. This is called ripple, because on an oscilloscope it looks like small ripples on the surface of a pond. The capacitor will smooth this out by absorbing energy at the high points and releasing it at the low spots. Basically, it just averages it all out, it can neither reduce or increase voltage on its own.
I assume you are considering a bare chip to save space and money. Besides a regulator, a bare chip needs other support: a clock crystal or resonator, an ICSP port to initially load a bootloader, and a serial, USB or FTDI interface to load sketches and see output. It quickly adds up. Rolling your own from scratch is a viable solution, but perhaps it would be better to wait until you have some more experience.
Instead, take a look at some of the smaller Arduino boards like the various Micro or Mini versions, or something like the Trinket or similar variants. That would be a much simpler way to save money and space.
Didn't think to check ebay. The specs look like this:
"Specs:
Input voltage: 3.2V-40V
Output voltage: 1.25V-35V
Maximum output current: 3A (Please ensure you use a heatsink above 2 Amps)
Maximum transfer efficiency: 92%
Switching Frequency: 150KHz
Module Size: (LxW) 43mm x 21mm"
So this looks good. But how would I limit the output voltage to 5 volts?
ShapeShifter:
No. A capacitor works with a voltage regulator, it cannot replace it.
So this looks good. But how would I limit the output voltage to 5 volts?
You would adjust it to 5V and leave it there. That little flat blue box with a screw head? That is a 10 turn potentiometer that adjusts the output voltage. Adjust it before connecting it to an Arduino.
polymorph:
You would adjust it to 5V and leave it there. That little flat blue box with a screw head? That is a 10 turn potentiometer that adjusts the output voltage. Adjust it before connecting it to an Arduino.
I was wondering what that was. Thanks. So once that is set at 5v, will is ALWAYS be at volts? Will ripples be consumed by the board itself?
HeyAwesomePeople:
I was wondering what that was. Thanks. So once that is set at 5v, will is ALWAYS be at volts? Will ripples be consumed by the board itself?
You've got the idea.
The silver cans are capacitors, they provide the required smoothing.
ShapeShifter:
I assume you are considering a bare chip to save space and money. Besides a regulator, a bare chip needs other support: a clock crystal or resonator, an ICSP port to initially load a bootloader, and a serial, USB or FTDI interface to load sketches and see output. It quickly adds up. Rolling your own from scratch is a viable solution, but perhaps it would be better to wait until you have some more experience.
Instead, take a look at some of the smaller Arduino boards like the various Micro or Mini versions, or something like the Trinket or similar variants. That would be a much simpler way to save money and space.
I can buy a chip with the bootloader on it and use the Arduino I already have to program it. I have never heard of needed a clock crystal or resonator. Could you please explain the use of those? I learned about using just the chip here: https://www.youtube.com/watch?v=30rPt802n1k and it seems to work fine with some power and the chip. I don't see why I couldn't do the same thing.
KenF:
You've got the idea.
The silver cans are capacitors, they provide the required smoothing.
Thanks. Please take a look at this diagram and tell me if it looks all good(attached to post)
I notice that for each transistor you have 4 LEDs in parallel with a Single one. I'm not sure how easy it's going to be to get these balanced.
In practice you'll find a voltage drop across the transistors (from the collector to the emitter). Once this is taken into account, I suspect your LEDs are going to be dimmer than you expect. But testing in circuit will give you a better idea.
KenF:
I notice that for each transistor you have 4 LEDs in parallel with a Single one. I'm not sure how easy it's going to be to get these balanced.
In practice you'll find a voltage drop across the transistors (from the collector to the emitter). Once this is taken into account, I suspect your LEDs are going to be dimmer than you expect. But testing in circuit will give you a better idea.
How would a voltage drop from the transister affect the LEDs brightness? At the end of each of the LED lines, there is atleast 3.2 or more volts left over. I am told the transistor may make it drop another .6v.
HeyAwesomePeople:
I am told the transistor may make it drop another .6v.
Actually, for a saturated transistor, 0.25V would be closer.
0.6V is the voltage drop on the base (to emitter), essentially the voltage drop of a silicon diode. When conducting, the collector can be pulled down lower than the base. This has many practical implications, almost all beneficial as it is in this case.
So you most certainly do not have to worry about using the same transistor to switch more than one LED chain - a long as you are supplying sufficient current to the base as you should here. But of course, you really should test it in practice by writing a sketch which switches the transistor on and keeps it on so that you can measure the collector voltage.
If it is the voltage adjust pot , doesn't that seem reasonable to expect ?
Haha, yeah, but I didn't want any random voltage spikes coming from it. But now I know the use of the capacitors on the switch.
Paul__B:
Actually, for a saturated transistor, 0.25V would be closer.
0.6V is the voltage drop on the base (to emitter), essentially the voltage drop of a silicon diode. When conducting, the collector can be pulled down lower than the base. This has many practical implications, almost all beneficial as it is in this case.
So you most certainly do not have to worry about using the same transistor to switch more than one LED chain - a long as you are supplying sufficient current to the base as you should here. But of course, you really should test it in practice by writing a sketch which switches the transistor on and keeps it on so that you can measure the collector voltage.
I'll start testing once I get the parts in. Thanks
KenF:
Hmm. Have to put something here if I just want to attach a picture.
I have attached a new schematic to this post. I do not understand why the negative output of the switching regulator goes right back to ground, instead into the negative input on the Arduino.
HeyAwesomePeople:
I have attached a new schematic to this post. I do not understand why the negative output of the switching regulator goes right back to ground, instead into the negative input on the Arduino.
Which is exactly the same thing! Except in your diagram it's no longer obvious that your transistors are ALSO connected to the arduino ground.
