[TriEmbed] Power Supply rail current

Shane Trent shanedtrent at gmail.com
Wed Jul 9 10:42:35 CDT 2014


If you are using Remote Sense you may want to connect the on-board sense
terminal to the output terminal with a 100 ohm resistor at the power supply
terminals to provide feedback if your remote sense wire becomes
disconnected. The pdf below has more on remote sense, Fig 6b.

I once had a developer at Borg Warner melt a 24V clutch unit under test
when the remote sense of their power supply line became disconnected. The
power supply also toasted my PWM FET module but I melted the unit under
test before my module failed. They were impress at how much power the PWM
module delivered before they it died!

http://www.astrodyne.com/wp/wp-content/uploads/AP_Remote_Sensing_AP6.pdf

Shane


On Wed, Jul 9, 2014 at 9:24 AM, Rodney Radford <ncgadgetry at gmail.com> wrote:

> Relays are rated at a specific amperage and as long as that amperage is
> not exceeded, you can open and close the contacts while current is flowing
> so that is really the best option
>
> Since this was a 1-off private build, for me, I would have checked the
> price of the larger capacity relays and if they were too high, I would have
> gone for a cheaper relay and just be careful that the current through the
> contacts is low at the time they are opened/closed.  That is a pain to do
> manually and I was just checking the supply specs to see if it has an
> inhibit on the output that can be used to control the supply to prevent it
> from supplying current until the relay is energized and it does not.
>
> Given that, just look for a high enough amperage relay - I would push
> beyond the 30A - perhaps to 50A for each of the legs.
>
> The supply does have remote sensing and I would recommend running that to
> the front panel.  That allows you to connect small wires to the load and it
> will measure the voltage at that point and control it to meet the desired
> voltage - so any voltage drop across the wires, relay, binding posts, etc
> will not be a factor.  Usually these are connected internally to the power
> supply outputs already, so you would need to remove that wire (specs don't
> say how to do that, but it is usually just a small wire that is cut or
> unscrewed) and then connect it to a set of binding posts on the front
> panel.  To make life easier for you in cases where you don't really care
> that much about exact monitoring, you can provide a front panel switch that
> connects the remote sensing back to the outputs on the front panel.  Just
> turn that to off and provide the wires to the load when you do care about
> exact voltae monitoring in high current situations.
>
>
>
> On Wed, Jul 9, 2014 at 8:08 AM, Jeffrey Crews <cruzetti at gmail.com> wrote:
>
>> Asking more for my own education than as a suggestion: could a large
>> enough capacitor prevent the arcing across the contacts as the relay opens
>> and closes? And if so, how large a capacitance would it take to handle this
>> much current?
>>
>> jsc
>>
>>
>> On Wed, Jul 9, 2014 at 8:01 AM, Adam Haile <email at adamhaile.net> wrote:
>>
>>> Ok, yeah, that's what I was thinking. I wanted it to be normally open
>>> and then energize the relay to close and provide power. That way when I
>>> turn the supply on, nothing is connected by default. But I assume I still
>>> have to be worried about the contact welding in that scenario since I might
>>> already have the device drawing power hooked up (I would rather not have to
>>> disconnect it every time I start up the supply).
>>>
>>> Also, I think I found my power rails:
>>> http://www.amazon.com/dp/B000H9JRI0/ref=biss_dp_t_asn
>>> 1/8" x 1/4" copper bar stock. My calculations show this should be able
>>> to handle WAY more power than I need. And it's pretty cheap. Figure I'd
>>> just do a slightly wider than 1/4" trace and then solder this on top.
>>>
>>>
>>> On Wed, Jul 9, 2014 at 4:19 AM, Scott Hall <scottghall1 at gmail.com>
>>> wrote:
>>>
>>>>  On 07/08/2014 05:50 PM, Adam Haile wrote:
>>>>
>>>> So,  let me make sure I understand this...
>>>> When you say have the relays energized, I know you mean energize the
>>>> solenoid but do you mean by that that the relay contacts are closed (power
>>>> flowing) or open (no power)? I'm guessing you mean don't go from open to
>>>> closed while there's power flowing since their will be a temporary arc?
>>>> Could I just use a normally closed relay and then use the microcontroller
>>>> to open the relay and cut the power if I need to.
>>>>
>>>>
>>>> For safety reasons, you want the relay to disconnect if energizing
>>>> power is removed.  An NC contacts will not break the circuit if you have
>>>> power control problems to the energizing coil.
>>>>
>>>>
>>>>  Do you have any links to those higher cost relays? I would really
>>>> love to actually make it so that I could have a button on the front (hooked
>>>> to the uC) that would allow me to, using the relay, turn the power on or
>>>> off to any of the outputs. So having one of these nicer relays, if not too
>>>> expensive, might be nice.
>>>>
>>>>
>>>> Look up "contactors" for relays designed for high currents and regular
>>>> switching.
>>>>
>>>>
>>>> --
>>>> Scott G. Hall
>>>> Raleigh, NC, USAScottGHall1 at GMail.Com
>>>>
>>>>
>>>> _______________________________________________
>>>> 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
>>>>
>>>>
>>>
>>> _______________________________________________
>>> 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
>>>
>>>
>>
>> _______________________________________________
>> 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
>>
>>
>
> _______________________________________________
> 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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.triembed.org/pipermail/triembed_triembed.org/attachments/20140709/8bab4856/attachment.htm>


More information about the TriEmbed mailing list