[TriEmbed] Need simple 1A controlled current power supply

Mon Sep 26 11:41:22 CDT 2016

Looks like there are versions with enable
<http://www.ebay.com/itm/SMAKN-LM2596-Dc-dc-Buck-Converter-Step-Down-Module-Power-Supply-Output-1-23v-30v-/272349260251?hash=item3f6947e9db:g:bt8AAOSwawpXurBE>
,

If you want to build it yourself, you can get inductors
<http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.X220uh+2A+toroid.TRS0&_nkw=220uh+2A+toroid&_sacat=0>
 eBay.
I use 2596 for <1A supplies with high input voltage, like the one below.

[image: Inline image 1]

On Mon, Sep 26, 2016 at 12:13 PM, Rodney Radford <ncgadgetry at gmail.com>
wrote:

> It would be great to find a board like this that had the on/off control
> pulled out so it can be controlled by the Arduino pin to turn on/off the
> magnet coil.
>
> That is the other part of the solution - not just 1A, but 1A I can pulse
> to a specific pattern.
>
> I know that part supports it, but all the boards appear to not support
> that feature. It is possible to cut the lead to the part and pull out that
> one pin, but I need something I can pass along to the students to build and
> I like simplicity.
>
> Have you seen any that have digital enable control, or an easy way to get
> that? The price point for these boards is definitely in the range of what I
> wanted to spend.
>
> Thanx,
> Rodney
>
>
> On Mon, Sep 26, 2016 at 11:56 AM, Robert Gasiorowski <rgresume at gmail.com>
> wrote:
>
>> 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 away.
>>
>> http://www.ebay.com/itm/5pcs-Re-DC-DC-3A-Buck-Converter-Adju
>> stable-Step-Down-Power-Supply-Module-LM2596S-/221991448900?
>> hash=item33afb8b144:g:d5YAAOSwX~dWktJo
>>
>> http://www.ebay.com/itm/DC-DC-3A-Buck-Converter-Adjustable-S
>> tep-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
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Triangle, NC Embedded Computing mailing list
>>>>> TriEmbed at triembed.org
>>>>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
>>>>> TriEmbed web site: http://TriEmbed.org
>>>>>
>>>>>
>>>>
>>>
>>
>
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