[TriEmbed] Need simple 1A controlled current power supply

[Robert Gasiorowski]

Here are couple of links for you. I use those for many things, it's cheaper
than building your own. Ping me if you need one right aw

http://www.ebay.com/itm/5pcs-Re-DC-DC-3A-Buck-Converter-
Adjustable-Step-Down-Power-Supply-Module-LM2596S-/221991448900?hash=
item33afb8b144:g:d5YAAOSwX~dWktJo

http://www.ebay.com/itm/DC-DC-3A-Buck-Converter-Adjustable-
Step-Down-Power-Supply-Module-LM2596S-/272254241762?var=&
hash=item3f639e0be2:m:mQbDIu3F52Dp9nEA1AhO84A

On Mon, Sep 26, 2016 at 11:24 AM, Rodney Radford <ncgadgetry at gmail.com>
wrote:

> Yes!  This is exactly the type of solution I was hoping to find.  I read
> through several on/off regulator specs over the weekend, but did not find
> one that could handle the 1A I needed (most were in the 100-200mA range).
>
> This is a good solution and pre-built boards with the necessary passive
> components are under $4 on eBay/Amazon.  I will order one to try out, but
> open to other suggestions as well.
>
> Thank you
>
> On Mon, Sep 26, 2016 at 10:21 AM, Robert Gasiorowski <rgresume at gmail.com>
> wrote:
>
>> Can I suggest LM2576 based switcher? There are plenty of them on eBay
>> for $1-$1.25.
>> You can feed them 12V and get 1.25V @ 3A. Then use resistor if you need
>> even lower voltage.
>>
>> Rob.
>>
>> On Mon, Sep 26, 2016 at 8:29 AM, Rodney Radford via TriEmbed <
>> triembed at triembed.org> wrote:
>>
>>> For the Southeastcon 2017 hardware robotics competition, one of the
>>> requirements is to be able to switch on and off a magnet field.
>>>
>>> The field is defined as number of turns, diameter, core, and the current
>>> - 1A - through it.  I need a simple (and cheap) way to implement this.  I
>>> will be building 8x of these for the competition and each school will be
>>> building one for their trial runs, so keeping it cheap and simple is better
>>> than elegant and higher cost.
>>>
>>> Initially I was planning on a very simple solution - a MOSFET switching
>>> current to the coil in series with a power resistor to drop the voltage.
>>> At first this was a 5 ohm, 5W power resistor (since the coil is below 0.1
>>> ohm), but then that changed to a 12 ohm, 12W power resistor as I switched
>>> over to using 12v to power everything since I needed that for the relays
>>> anyway (for another part of the design).
>>>
>>> This works, and is cheap and easy to build and if the coil is only on
>>> for a few seconds at a time, this is a great solution. However, a change in
>>> the contest stated that the coil is initially powered on (so robots can use
>>> it to navigate to the coil) and if the robot fails, it could be on for the
>>> full duration of the 5 minute competition.
>>>
>>> I tested this last night and it does work, but 12w through even a metal
>>> power resistor is HOT after about 30 seconds.  I would hate to use this for
>>> 5 minutes.  The cost is good - below $2 for the MOSFET and power resistor -
>>> but I am looking to see if there is a better solution.
>>>
>>> Some ideas considered:
>>> * use a lower voltage - would work, but I would need a lower voltage 1A
>>> supply
>>> * use a switched regulator - get the lower voltage *and* ability to
>>> control it
>>> * others?
>>>
>>> Any thoughts / suggestions?
>>>
>>> Btw, I will be bringing this in to the next meeting (next R&A/TAR and
>>> next Triembed) to show the progress on the hardware and software design.
>>> Most of it is done now and I hope to finish it in the next few days.
>>>
>>> On another issue - I watched a couple Eagle videos this weekend and was
>>> able to complete the schematic capture for the board and even routed a PCB.
>>> The routes were done with the auto-router and they were ugly, but
>>> functional. Not sure if I will just route it myself, or route some and let
>>> the autorouter finish, etc, but I need to investigate the design rules for
>>> the fab house first to verify I have spacings, hole sizes, trace widths,
>>> etc are correct before I dump too much more time into it.
>>>
>>> Thanx,
>>> Rodney
>>>
>>>
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>>>
>>>
>>
>
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