Hello everyone
I'm using this MT3608 to boost the voltage from 4.2V (the battery fully charged voltage) to 12V (for reading some RS485 sensors). It is ok for reading one sensor, but now I've noticed that the output current of the MT3608 is not enough for reading multiple sensors. How can I boost the output current of the MT3608?
here is the datasheet of the MT3608:
MT3608.pdf (597.7 KB)
Hello navidh91
Take a search engine of your choice and ask the WWW for 'MT3608 alternative' to collect some data to be sorted out to get the needed information.
Have a nice day and enjoy coding in C++.
So, are you using this as a chip in something you made or is it something you bought?
Have you measured a voltage drop on the 12V line as you add extra sensors?
Normally a TTL / RS232 converter chip contains its own capacitave voltage booster anyway and there is no need to supply it with a separate supply.
How many sensors is that before you start to see problems?
im using the chip in my own circuit.
the sensors are connected in parallel so i dont think there will be a voltage drop issue when i want to add more sensors.
i haven't seen that kind of TTL/RS232 converters that gives 12v output.
i was only able to run one sensor and when i try to add one more sensor i got a current problem
Post a schematic and a picture of the hardware setup.
here is the schematics and PCB
OK.
How have you made this?
Is it on a PCB?
If not you don't stand a cat in hell's chance of getting much current from it.
I have managed many experienced power supply professional engineers in my time and I have never found one that could layout a PCB for a voltage booster in less than three attempts.
Layout is absoloutly vital to the running of the circuit, along with the choice of the correct grade of ferrite in the coil windings and the correct type of capacitors. The ones you get on eBay on a PCB are rubbish as well.
It's physics, the more sensors the more current, and when you exceed what your supply can give, the voltage will drop.
So what chips are you using, in my experience they all provide their own high voltage. Like the MAX232 to name just one.
i use this converter
So you are using RS485, why did you tell us you were using RS232?
There is a world of difference between the two.
How much current does one module require? What is the maximum number of modules you will use at one time?
You should not be supplying this chip with 12 V.
The data sheet says it is a stress rating only
The parameters are all defined with a Vcc of 5V.
So supplying it with 12V is killing it.
As far as I noticed, each sensor has a maximum current of up to 200mA at the moment of reading.
if you mean TTL/RS485 Converter, i just connected it to 5V and i just use this module for reading the data of sensors. each sensor needs 12V-24V range that the voltage of sensors provides separately with MT3608 chip
i just want to boost the output current of MT3608 IC, this is my solution.
so if you know some kind of current booster circuit that is able to boost from 1A to 2 or 3A it will be great to send me the circuit
No you don't get it. You can't boost the current, unless you start with higher voltage.
And that voltage source has to be able to supply enough current, for it to work. So for example if you had a Voltage source that was twice as high as the voltage you wanted to end up with then it would have to supply half the current, plus an efficiency rating of your converter of about 80%.
Do you not have specifications for these sensors?
The datasheet suggests your converter should be good for up to 2A:
But, as @Grumpy_Mike suggests, achieving that will rely on expert PCB design - designing switch-mode power supplies is not a beginner's task.
So how have you tested your design?
Note that 2A at 12V would mean that it pulls 6A from your battery - are you sure the battery is coping with that? And is your input wiring up to that?
While the data sheet says it will delver 2A, that is not at any voltage input, that is at a much higher input voltage compared to your output voltage. Say for example 10V in and 12V out.
Note this diagram from the data sheet
In effect this is saying with the best possible design you can only get 800mA output for a boost factor of 5V to 12V.
Do you know what current you are actually getting at the moment?
There's no point trying to boost it if you're already at the maximum capability of the chip!
And there's no point just talking about an unspecified "boost" - you must determine what current you actually need to deliver.
And if that current is more than the MT3608 can provide, then you'll need to choose another chip.
For testing, if you replace your design with a known-good 12V power supply - does it work?
If not, you (also) have other problems to solve...
What you need to do is to take your power supply and plot a graph of output voltage against output current, and see how this holds up. Use resistors of 60Ω to draw successive 200mA steps.
This will tell you how good your actual implementation is.
