I have an issue with powering multiple heated gas sensors and Arduino. My gas sensors require 5V as an absolute minimum, so once the voltage drops as low as 4.88V they stop working. Each sensor consumes ~0.3A when they heat-up, plus the Arduino has a set of LEDs attached.
I use an external power source to power the sensors and Arduino separately. My issue is all my power sources that I tried, have failed to produce the stable 5v. They do start with providing that, even when all the sensors are heating, but once the Leds turn on, the voltage drops to 4.88V and the sensors shut down. To avoid that, I set my DC-DC Power Module (rated as 25W, running from an array of 6 AA batteries), to produce ~5.46V, then when the voltage still drops slightly my sensors wouldn't go off. The same behaviour I observe when I power from a wall USB charger, rated to 2A, and supposed to produce 5V.
So here is my question: is there a simple way to use some sort of a transistor/regulator to produce a voltage level that never drops below 5V? Would it be possible to achieve that with a 2A USB wall charger as a power source?
I could use for that the DC-DC Power Module, that I mentioned, but the main issue with that one is it is large, and I'd rather need something more compact. Besides, when I set it to 5V (it has a built-in switch Variable out/5V) the power still drops below 4.9V...
The Leds i guess are powered through your arduino board right ? If you use seperate power sources how can the gas sensors be affected by the Leds ? What power sources do you use for each one ? how many volts is each ?
zaxarias:
The Leds i guess are powered through your arduino board right ? If you use seperate power sources how can the gas sensors be affected by the Leds ? What power sources do you use for each one ? how many volts is each ?
Sorry, I was not really clear on that By "separate", I meant a single power source that powers arduino and [separately] the sensors and the leds. Sensors and leds consume 1-1.2A in total, which is AFAIK beyound of what Arduino can handle, that is why I attached them separately from arduino to the DC module, but still they obviously can affect each other.
zaxarias:
The Leds i guess are powered through your arduino board right ? If you use seperate power sources how can the gas sensors be affected by the Leds ? What power sources do you use for each one ? how many volts is each ?
Sorry, I was not really clear on that By "separate", I meant a single power source that powers arduino and [separately] the sensors and the leds. Sensors and leds consume 1-1.2A in total, which is AFAIK beyound of what Arduino can handle, that is why I attached them separately from arduino to the DC module, but still they obviously can affect each other.
fungus:
Why do you connect the sensors to the buck converter? Why don't you connect them directly to the batteries?
Use the converter for just the Arduino+LEDs.
What LEDs are they? You'd need an awful lot of LEDs to cause a voltage drop (unless you're connecting them wrong).
I don't know if they can handle 9V... But the thing is, that initially I wanted to power my little device from the 2A USB wall charger, and even that one had also turned off one of the sensors once the LEDs lit up... But thanks, for the hint, I didn't think of it. I will check the specs on the sensors if they allow a larger input (may be I use an array of 4 batteries instead, that would give 6V).
nikodll:
I don't know if they can handle 9V... But the thing is, that initially I wanted to power my little device from the 2A USB wall charger, and even that one had also turned off one of the sensors once the LEDs lit up... But thanks, for the hint, I didn't think of it. I will check the specs on the sensors if they allow a larger input (may be I use an array of 4 batteries instead, that would give 6V).
a) Batteries don't give 1.5V, especially under heavy load. (measure one and see!)
b) Speaking of measuring, it's time you got your multimeter out and measured the amps coming out of the batteries when the LED comes on.
nikodll:
I wanted to power my little device from the 2A USB wall charger,
It should work.... once you figure out what's wrong in the circuit. Something is sucking far more power than it should.
fungus:
a) Batteries don't give 1.5V, especially under heavy load. (measure one and see!)
...
It should work.... once you figure out what's wrong in the circuit. Something is sucking far more power than it should.
I used Adafruit USB Power Gauge Mini-Kit, to see how much does it suck from the adapter. That thing shows 4 (sometimes 5) Watts in total. Meaning no more than 1A... but it is a Samsung phone charger, who knows what did they put in there.... And from the batteries, it's like they are weak and the voltage drops, but the DC module does not react on it.
Theres your problem, its a charger, not a regulated power supply, different output characteristics.
Question, can you clarify this for me.
Do you have a regulated 5V supply for the sensors and another completely independent regulated supply for the arduino?
Or a regulated 5V supply powering the sensors and the arduino?
Please post a CAD or picture of a hand drawn circuit diagram of your project, in jpg, png or pdf thanks.
zaxarias:
There are voltage regulators for either 5V or 6V..
I wonder how those would react, if the voltage slowly drops from 9V to 8.5V... would the output stay the same 5V or will it fluctuate?
An example of a 5V regulator is L7805CV ,it has a maximum input voltage of 35V and outputs 5V..
So if the voltage drops it will keep on supplying 5V on the output.
So if I feed in something between 9 and 12 volts, it should produce stable 5V. Maybe there is another one that works with the range of 6..10V, so it would work with the weak batteries, producing the 5V that the sensor needs. Or your point was that I am missing something important here?
fungus:
Are you sure you know what a voltage regulator does...?
So if I feed in something between 9 and 12 volts, it should produce stable 5V. Maybe there is another one that works with the range of 6..10V, so it would work with the weak batteries, producing the 5V that the sensor needs. Or your point was that I am missing something important here?
If the input voltage of the L7805CV is between 7V-35V, it will give to the output 5V.. It's that simple.. Hope you understand ..
TomGeorge:
Theres your problem, its a charger, not a regulated power supply, different output characteristics.
Ok, so the wrong choice of the power source in this case. But why does the voltage drop from 5.0V to 4.88V when I use a battery through a step-down converter? I thought it should act similar to a voltage regulator? If I try one instead, like people here suggested, would I see a similar decrease in voltage?
nikodll:
Ok, so the wrong choice of the power source in this case. But why does the voltage drop from 5.0V to 4.88V when I use a battery through a step-down converter? I thought it should act similar to a voltage regulator? If I try one instead, like people here suggested, would I see a similar decrease in voltage?
Why don't you measure the voltage and current on both sides of the converter?
If the output is drooping, EITHER the regulator isn't regulating well enough
(which is either because its crap or the input voltage has fallen too low),
OR there is too much resistance in the wiring from the regulator to the sensors
(or both).
For several amps at low voltage you need thick wires, and if the cable run is long you
will need very thick wires.
All of this is solved by connecting the regulator output directly to the sensor,
short wires, negligible resistance losses. This is called Point-of-Load regulation
and its usually the best way to do things.
Note that different regulators are different and you should check the datasheet for
the specs (most 5V regulators only guarantee to be somewhere between 5.25 and 4.75V
note, not good enough for your application.)
TomGeorge:
Theres your problem, its a charger, not a regulated power supply, different output characteristics.
Ok, so the wrong choice of the power source in this case. But why does the voltage drop from 5.0V to 4.88V when I use a battery through a step-down converter?
When you use the usb as power supply the voltage is exactly 5.0 v ?
By "separate", I meant a single power source that powers arduino and [separately] the sensors and the leds. Sensors and leds consume 1-1.2A in total, which is AFAIK beyound of what Arduino can handle, that is why I attached them separately from arduino to the DC module, but still they obviously can affect each other.
