I would like to use arduino (preferably the mini) to control a boost converter in order to generate at least 10 volts and 10 amps from two 3.7 volt 18650 batteries. I can find a lot of adjustable boost converters but most of them in the 10 amp range are manually (via an adjustment screw) or way to big. I need all of it to fit into roughly a 5 x 3 x 1 inch enclosure. The dimensions can be adjusted if necessary. But anyhow, I'd like to be able to control the voltage output and 10 amps has be able to be tolerated within the IC or circuit. Whether its all controlled via PWM or whatever I just need to be able to change the voltage as needed on the fly. You have to walk me through it. I just need some direction to work in or an idea. Perhaps I would be better off building my own converter circuit? Just some advice would be greatly appreciated. Oh and I'm waiting to buy the arduino board until I get all the components figured out as some boards are limited in what they provide.
Good job because that is a property of the load not the power supply and so impossible to do.
Perhaps I would be better off building my own converter circuit?
How good are you at electronics?
That is a very difficult / impossible project for a beginner. You will have to use a PCB and get the design right. I have never known a professional power supply engineer get it right first time, it normally takes three iterations.
but most of them in the 10 amp range are manually (via an adjustment screw)
You can normally replace that with a varying voltage from the smoothed PWM of an arduino.
or way to big.
Yes your size requirements are pushing it but just about possible.
By the way how long do you want the batteries to last?
How good are you at electronics?
That is a very difficult / impossible project for a beginner. You will have to use a PCB and get the design right. I have never known a professional power supply engineer get it right first time, it normally takes three iterations.
Like you said I'm a beginner, so I'll take your word for it and count that option out.
You can normally replace that with a varying voltage from the smoothed PWM of an arduino.
That's super handy to know thanks!
Yes your size requirements are pushing it but just about possible.
Okay, if I need to I can adjust the dimensions. Nothing is set in stone yet.
By the way how long do you want the batteries to last?
The batteries are also negotiable. Whatever batteries will do the best job and fit into the enclosure. I would like for them to last for at least 8 hours intermittently operating at 8-10 volts and 6-10 amps for maybe 5-10 minutes at a time. Maybe spaced out every 30 minutes.
Hi, what is the load, and what is the project that needs this sort of control and power?
It's a vaporizer. The load is going to be the atomizer which should be about 0.6 ohms. I realize they sell these things already. But, I want more control over the quality and the features, such as short protection and over current. Also, I'm trying to hit 50 watts.
If you can get > 10 amps from two lithium batteries. ..
I'm betting you'll have a few minutes not 10-15... what's the capacity? The best I've seen is around 1a/h unless you spend big bucks.
The Sony VCT5 18650 are supposedly rated at 30 amps max. And have a capacity of 2.6a/h for about 20 bucks. And I've heard good things about them from friends. Though I don't think any of them have tried to achieve what I am. Also, a few minutes of discharge at 10 amps should be enough so long as the charge lasts.
Hi, what do they already use to power the vapouriser, and is it an air pump type or a ultrasonic type.
If you want to control the speed of a motor, then it maybe easier and more efficient to use PWM motor control, rather than try and control a SMPS power module.
I'm doin' a similar kind of project with arduino too There's a way to minimize the size of the converter. It's just to increase the frequency of the switching component in a boost circuit (May be MOSFET, BJT, IGBT etc.). The frequency will reduce both ripple current and ripple voltage so you can reduce the size of the inductor and the capacitor.
In commercial, the frequency might be very high (1MHz) which arduino is capable of but I don't think that a cheap switching component would.
Hi, what do they already use to power the vapouriser, and is it an air pump type or a ultrasonic type.
If you want to control the speed of a motor, then it maybe easier and more efficient to use PWM motor control, rather than try and control a SMPS power module.
This type of vaporizer use current to heat up coils which in turn vaporizes liquid.
I'm doin' a similar kind of project with arduino too smiley-grin There's a way to minimize the size of the converter. It's just to increase the frequency of the switching component in a boost circuit (May be MOSFET, BJT, IGBT etc.). The frequency will reduce both ripple current and ripple voltage so you can reduce the size of the inductor and the capacitor.
In commercial, the frequency might be very high (1MHz) which arduino is capable of but I don't think that a cheap switching component would.
Are you building your own converter circuit? As Grumpy_Mike pointed out, I'm a beginner. I don't know if I'd have the skills to build a circuit that would suit my purposes or be small enough to fit int a 5 x 3 x 1 enclosure.
So a lot of the converters I can find that are capable of 10-12 volts dont reach the 10 amps I need. The ones that do meet the 10 amps require a much higher input voltage (10 volts and higher) that I could not achieve from the 3.6 volt VCT5 batteries without stepping the voltage up. How could I increase the current even further?
I have a theory. Feel free to explain how close or wrong I am. Could I use one converter to step up the voltage first to feed the high input voltage of a second which then adjusts it to the required voltage and current? To elaborate, the batteries are 3.6 volts which feed into a converter which bumps the voltage and current up to 12 volts at say 4 amps. That is then fed into a converter which bumps up the current to 10 amps and then can be adjusted via PWM as needed. I'm trying to get a grasp on this, so if I'm way off please tell me why. This doesn't seem very practical do to the space I need it to fit into.
Also if anyone has a suggestion on IC's, converters or anything else that can do this PLEASE point me in the right direction. Ultimately, all I want is ~50 watts (or close to it) that can be adjusted down or back up as needed depending on the requirement.
That is quite a lot to ask for. That means you will be pulling 14 to 15 amps from that battery, are you sure your battery can provide that?
There is no way a two stage approach will work you must do it in on step.
Also I can not understand what the Arduino will be doing, there seems to be no job for it to do.
Look at chips that do boost regulators, you will have to use an external FET to get the current so don't look for a chip with an output rating of 10 Amps because you will not find one.
the frequency might be very high (1MHz)
The problem with that is the coil, and the magnetic saturation.
If you have fix resistance of your vaporizer heat up coils (0.6 Ohms), you do not need to have adjustable boost converter.
P = R x I2 and you have P = > 50W , R = 0.6 Ohms, all you need is to adjustable current.
If your battery have 8.4V with 0.6 Ohms , if will have max of 14A current, you just need to control the current with the PWM and logic level MOSFET with Arduino will do.
That is quite a lot to ask for. That means you will be pulling 14 to 15 amps from that battery, are you sure your battery can provide that?
I think so. The batteries are rated at 30 amps max.
There is no way a two stage approach will work you must do it in on step.
I didn't think so. It sounded ridiculously impractical.
Also I can not understand what the Arduino will be doing, there seems to be no job for it to do.
Arduino's job would be to provide a visual (via lcd) of the information (ie power, resistance, voltage, maybe battery life), allow manual input of the power output needed (via buttons) and then adjust the voltage and current, automatically, to create the appropriate power to the coils. I especially need it so it can account for the change in resistance as the coil inevitably increases resistance due to the amount of wear and gunk build up and adjust the voltage and current accordingly. Also, I want arduino to prevent discharge: once the battery falls below a certain charge, coils reach a certain resistance (time for new coils) and possibly other protective measures.
Look at chips that do boost regulators, you will have to use an external FET to get the current so don't look for a chip with an output rating of 10 Amps because you will not find one.
...you just need to control the current with the PWM and logic level MOSFET with Arduino will do.
Okay, so to clarify, use a boost converter to adjust the voltage as required and a MOSFET to adjust the current? And both of these can be controlled via Arduino using PWM?
Hi, your battery is rated in Ah, or AmpHours, what is your battery rated.
Don't forget that each time you power convert you will loose power due to inefficiencies.
How was the vapouriser meant to be powered. AC or DC supply?
I especially need it so it can account for the change in resistance as the coil inevitably increases resistance due to the amount of wear and gunk build up and adjust the voltage and current accordingly.
I don't think that will happen.
The resistance of the coil will increase with temperature but it will not be affected by anything building up around it. Resistance is a bulk effect in the metal. If anything build up of stuff around it is only going to reduce the resistance very slightly, if anything at all.
Okay, so to clarify, use a boost converter to adjust the voltage as required and a MOSFET to adjust the current? And both of these can be controlled via Arduino using PWM?
No.
You apply a PWM signal though a FET to control the average current through the coil.
There's a way to minimize the size of the converter. It's just to increase the frequency of the switching component in a boost circuit (May be MOSFET, BJT, IGBT etc.). The frequency will reduce both ripple current and ripple voltage so you can reduce the size of the inductor and the capacitor.