Topics

reverse polarity protection (ubitx.net)

Mike Woods
 

MVS Sarma

Thank you!  I am uploading now.

Mike


On 8/08/18 11:02 PM, Mvs Sarma wrote:
Here is a more meaningful diagram

On Wed, Aug 8, 2018 at 4:17 PM Mvs Sarma <mvssarma@...> wrote:
I got your point Mike
 I shall upload a suitable diagram with jack more understandable.


On Wed, Aug 8, 2018 at 1:17 PM Mike Woods <mhwoods@...> wrote:
MVS Sarma

It is the drawing of the jack that people are referring to, not the positioning of the fuse!
The vertical bar would normally represent the sleeve - and you have this connected to the fuse and on to +12v?   Shouldn't the sleeve and the tip be reversed in the diagram?  Or do you normally have the sleeve positive and the tip negative (some people do - but most don't) in which case the diode is shown incorrectly!

73
Mike

On 8/08/18 12:34 AM, Mvs Sarma wrote:
Sarma surely responds.
 The reverse protection diode has been shown in the ubitx sch , both v3 and v4 perhaps.
 I would only suggest that let us have a fuse in series to dc of say 5 amps. the reverse diode would sit after the fuse to ground.
 Any accidental reverse connection , the fuse would blow and reverse voltage would not continue to the actual circuit, once fuse blows.


Regards
MVS Sarma
 

On Tue, Aug 7, 2018 at 1:56 PM, Mike Woods <mhwoods@...> wrote:
Jonathan

I will add PH2LB's reverse voltage protection solution to that page at your suggestion.  I hadn't noticed that idea previously, but did recognise the distinctive build so I guess it is on ubitx.net somewhere.

I am not sure about the diagram from MVS Sarma.  Let's wait and see whether he responds?   He may care to redraw the diagram if he agrees!  Everybody seems to draw those sockets differently ...

73

Mike ZL1AXG ubitx.net


On 7/08/18 2:58 AM, Jonathan Washington wrote:
Hi there,

In wiring my µBITX based on the guides and notes available at hfsignals.com, ubitx.net, this group's wiki, and the like, I noticed a discrepancy related to reverse polarity protection.

I believe the diagram with included fuse by MVS Sarma at https://ubitx.net/ubitx-fix-reverse-polarity-protection/ has the jack wired in reverse (- tip, + sleeve) of the standard (+ tip, - sleeve).  I suppose wiring it this way could be a good way to test if the fuse will do its job!

I should note that this solution seems preferable to the solution(s) provided in W4RJP's wire-up diagram (v1.9) posted at https://groups.io/g/BITX20/wiki/UBITX-Assembly , where it looks like the fuse and the diode would both blow in the case of reverse voltage, and the reverse voltage would still flow through the µBITX.  In MVS Sarma's solution, my understanding is that only the fuse would blow, and the µBITX wouldn't be exposed to any reverse voltage.

Also, I wonder if Mike might consider adding to the reverse polarity page PH2LB's reverse polarity protection solution from here:

I haven't tried it yet, but it seems ridiculously simple, and reasonably effective.  I'd probably still want to add a fuse with that solution, though, to protect against accidental shorts.


Jonathan, KD5CFX


--
Mike Woods
mhwoods@...


--
Mike Woods
mhwoods@...


--
Mike Woods
mhwoods@...

MVS Sarma
 

the original Idea is from Pete.
 we only added a fuse instead of direct diode  not to allow a fireball in the enclosure, Mike.
 Thanks and regards
sarma
 vu3zmv

On Thu, Aug 9, 2018 at 1:37 PM Mike Woods <mhwoods@...> wrote:
MVS Sarma

Thank you!  I am uploading now.

Mike


On 8/08/18 11:02 PM, Mvs Sarma wrote:
Here is a more meaningful diagram

On Wed, Aug 8, 2018 at 4:17 PM Mvs Sarma <mvssarma@...> wrote:
I got your point Mike
 I shall upload a suitable diagram with jack more understandable.


On Wed, Aug 8, 2018 at 1:17 PM Mike Woods <mhwoods@...> wrote:
MVS Sarma

It is the drawing of the jack that people are referring to, not the positioning of the fuse!
The vertical bar would normally represent the sleeve - and you have this connected to the fuse and on to +12v?   Shouldn't the sleeve and the tip be reversed in the diagram?  Or do you normally have the sleeve positive and the tip negative (some people do - but most don't) in which case the diode is shown incorrectly!

73
Mike

On 8/08/18 12:34 AM, Mvs Sarma wrote:
Sarma surely responds.
 The reverse protection diode has been shown in the ubitx sch , both v3 and v4 perhaps.
 I would only suggest that let us have a fuse in series to dc of say 5 amps. the reverse diode would sit after the fuse to ground.
 Any accidental reverse connection , the fuse would blow and reverse voltage would not continue to the actual circuit, once fuse blows.


Regards
MVS Sarma
 

On Tue, Aug 7, 2018 at 1:56 PM, Mike Woods <mhwoods@...> wrote:
Jonathan

I will add PH2LB's reverse voltage protection solution to that page at your suggestion.  I hadn't noticed that idea previously, but did recognise the distinctive build so I guess it is on ubitx.net somewhere.

I am not sure about the diagram from MVS Sarma.  Let's wait and see whether he responds?   He may care to redraw the diagram if he agrees!  Everybody seems to draw those sockets differently ...

73

Mike ZL1AXG ubitx.net


On 7/08/18 2:58 AM, Jonathan Washington wrote:
Hi there,

In wiring my µBITX based on the guides and notes available at hfsignals.com, ubitx.net, this group's wiki, and the like, I noticed a discrepancy related to reverse polarity protection.

I believe the diagram with included fuse by MVS Sarma at https://ubitx.net/ubitx-fix-reverse-polarity-protection/ has the jack wired in reverse (- tip, + sleeve) of the standard (+ tip, - sleeve).  I suppose wiring it this way could be a good way to test if the fuse will do its job!

I should note that this solution seems preferable to the solution(s) provided in W4RJP's wire-up diagram (v1.9) posted at https://groups.io/g/BITX20/wiki/UBITX-Assembly , where it looks like the fuse and the diode would both blow in the case of reverse voltage, and the reverse voltage would still flow through the µBITX.  In MVS Sarma's solution, my understanding is that only the fuse would blow, and the µBITX wouldn't be exposed to any reverse voltage.

Also, I wonder if Mike might consider adding to the reverse polarity page PH2LB's reverse polarity protection solution from here:

I haven't tried it yet, but it seems ridiculously simple, and reasonably effective.  I'd probably still want to add a fuse with that solution, though, to protect against accidental shorts.


Jonathan, KD5CFX


--
Mike Woods
mhwoods@...


--
Mike Woods
mhwoods@...


--
Mike Woods
mhwoods@...

Mike Yancey
 

Ah - the ol' internal diode - it goes in the direction of *correct* power.

When reversed, it is also reversed. See:
https://hackaday.com/2011/12/06/reverse-voltage-protection-with-a-p-fet/

Or Afroman's video:
https://www.youtube.com/watch?v=IrB-FPcv1Dc

Mike Yancey, KM5Z

MVS Sarma
 

in the first link you have indicated,  Generally pmosfet as a switch for +ve voltage is applied with source towards supply and Drain other side.
please see the link

 Hence I am unable to visualize the schematic at link i\1 in your post
regards
sarma
 vu3zmv


On Fri, Aug 10, 2018 at 7:59 PM Mike Yancey <mikeyancey@...> wrote:

Ah - the ol' internal diode - it goes in the direction of *correct* power.

When reversed, it is also reversed. See:
https://hackaday.com/2011/12/06/reverse-voltage-protection-with-a-p-fet/

Or Afroman's video:
https://www.youtube.com/watch?v=IrB-FPcv1Dc

Mike Yancey, KM5Z