Needing to boost amps and voltage

[DanielHowden]

I am writing a system the uses an Arduino as the logical side of things. I need it to push out 12 volts and 5 amps but the Arduino will only push 5 volts and milli amps. I have read that I could use a MOSFET but also read that they do easily overheat and shut down until they cool. Thinking about it maybe all they need is a heatsink. However, I don't know if they will push the amps up also and how I would control the boost in volts and amps. The other option would be to use a step up board which I have tried and it does give me a step up to a steady 12 volts but the amperage is still in the milli amps so this does not solve the problem.

Any advice or direction for reading material would be greatly appreciated.

Thanks, Daniel.

 

[Nigel Goodwin]

You're probably confusing yourself, particularly with the title of this thread.

You don't 'boost' anything - you simply need a supply capable of the required voltage and current, and use the Arduino to switch it ON and OFF. The simplest way would probably be a relay, but you could use a MOSFET or bipolar transistors. Also, MOSFET's don't 'easily overheat', nor do they 'shutdown'.

A lot really depends EXACTLY what you're trying to do, different methods have advantages for different tasks.

 

[DanielHowden]

Ah ok, thank for the reply. I did try to push the output from the step up board to a 12 volt relay and there wasn't enough to switch it, also I think a relay would be too slow in operation. I am trying to produce a spark from a 12 volt coil and that should ideally get 5 amps when I am currently not even pushing one amp.

 

[Nigel Goodwin]

As I said, you're not wanting to 'stepup' anything, you need an existing 12V high current source and some kind of switching device.

But you're still far too vague, you want 'a spark' - that's just ONE - presumably you want more than one?, so how often do you need them, and for how long. This I why I said EXACT, just feeding bit's and pieces at a time will take ages.

 

[crutschow]

An N-MOSFET with sufficient voltage and current rating will work for that purpose.
The voltage rating must be high enough to give the spark voltage you want.
For example, if you have a typical 100:1 ignition coil, than 100V rating on the primary will tive 10,000v on the secondary.
The MOSFET current rating should be at least twice the maximum coil current.

The MOSFET would need to be a logic-level type device (Vgs threshold max ≤ 2V) so it fully turns on from the 5V output from the micro.
A standard MOSFET won't work.
Also you need to add a Zener across the MOSFET drain-source rated at about 80% of the MOSFET maximum voltage rating, to protect the MOSFET from the output voltage spike generated by the coil when the MOSFET shuts off.

 

[audioguru]

A Mosfet gets hot when driving only 5A when it is not switching completely on. When the gate of a logic-level Mosfet is driven with 4.5V or more pulses it switches completely on so that it barely gets warm. An ordinary Mosfet is spec'd with 10V gate pulses.

 

[Reloadron]

A Google of arduino mosfet circuit diagram will bring up plenty of schematics including some actual pictorials like this one. I suggest using a RFP30N06LE MOSFET which can be had for about $1.00 USD. Just replace the motor shown in the latter link with your load.

Ron

 

[DanielHowden]

Wow, sorry for the late reply, I have been working away.

So Nigel, sorry that I am still not giving the information you need. I'm not very good at transferring whats in my head to the written word. I will have a 12v battery in the mix and I will want to spark the plug many times as I want to run an engine. If you have a solution that will allow the 12v battery to be used as the power source and I just need a low voltage switch then that sounds interesting.

Thanks for all the info about the MOSFET, and Ron, I took a look at your links and I will take the time to read these through. I still don't understand how the voltage is regulated through the MOSFET but maybe this question will be answered when I read you link.

Thanks, Daniel.

 

[Nigel Goodwin]

Wow, sorry for the late reply, I have been working away.

So Nigel, sorry that I am still not giving the information you need. I'm not very good at transferring whats in my head to the written word. I will have a 12v battery in the mix and I will want to spark the plug many times as I want to run an engine. If you have a solution that will allow the 12v battery to be used as the power source and I just need a low voltage switch then that sounds interesting.

Thanks for all the info about the MOSFET, and Ron, I took a look at your links and I will take the time to read these through. I still don't understand how the voltage is regulated through the MOSFET but maybe this question will be answered when I read you link.

Thanks, Daniel.

You don't 'regulate' using the MOSFET, that just switches the 12V to the coil. You power the Arduino from the same 12V - or via a regulator from the 12V.

However, what has the Arduino got to do with an ignition system?, which I presume is what you're looking for?.

 

[DanielHowden]

Yes, I want to mess around with ignition timing. So you are saying that the MOSFET is used as a switch then right?

I have no idea how to do that so I will have to research this area.

I did find out the the Arduino can accept 12v as a power current but the output will only be 5v still as a max, I don't understand how I arrive at the 12v to the ignition coil, sorry.

Daniel.

 

[ChrisP58]

We could probably help you better if we had a better understanding of what you're trying to accomplish. As in the whole picture of the end goal

There have been many threads on this forum where the original post was a difficult part of what the poster thought he needed. Then, after 50 complex questions, we finally find that something simple would have fulfilled his need.

 

[Mickster]

We could probably help you better if we had a better understanding of what you're trying to accomplish. As in the whole picture of the end goal

There have been many threads on this forum where the original post was a difficult part of what the poster thought he needed. Then, after 50 complex questions, we finally find that something simple would have fulfilled his need.

This post (mine) is takings things further off-topic and may need to be split to the site issues/feedback section...

As ChrisP58 and many other members are having to point out, in ever-increasing numbers, it almost appears that an OP is working on some super Top-Secret project and divulging anything more than a scant description is taboo. At this point, garbage in = garbage out. It's not until a whole heap of teeth-pulling is done, in posts spanning multiple pages, that the actual details which matter are produced. That is the point where the real help can then be provided.

It's been over 10 years since I joined ETO and the registration procedure is obviously a distant memory. I'm sure there is a welcome message that directs new members to read the terms and conditions, and perhaps mentions FAQ's and stickied posts, but maybe new members skip that long welcome message because they just want an answer...

Can a Mod or Admin, or even a new member, provide a link to the current welcome message, so that we can collectively try to tweak it and make absolutely clear that max info is key to success here?

EDIT: No disrespect meant to DanielHowden in this post, this thread is one of the shorter information-gathering exercises. It just happens to be a response to Chris's observations, which a lot of long-time members appear to be highlighting of late.