[Guide] Graceful shutdown switch without Pololu [RETIRED]

[tronicgr]

I would use a reed switch to have it hidden from view, so it will activate the reset by placing it near a strong magnet...

Thanks
Thanos

[Camble]

Turns out there's not really enough room to fit a reset button in beside the power switch. Not on-board anyway. It could be done, but it's not gonna fit neatly under the slide cover.

I've added the reset headers to the board regardless.

[SidSilver]

Too bad

[hueblo]

Hey @camble

While waiting for your circuit to be ready I decided to build your shutdown circuit using the DMG switch. Because I'm a visual person I put the image below together based on your dmg diagram and the conversations in the thread. Is it correct? does the resistor positioning matter if its before the JFET or after?

(I used paint, thats all I have access to at work)
Deleted it so people do not get confused

[RxBrad]

@hueblo

Hmm... I just built mine (haven't tested it yet), but where you have the wires attached to the switch, I swapped the blue and purple wires. I also swapped the order that the resistor and GPIO4 (and resistor & GND) are connected in the circuit (but I honestly don't know enough about circuits yet to know if that matters).

For me, when the GBZ is off, GPIO24 (I actually used 27 per the first post) & 3.3V have continuity. When the GBZ is on, EN and the drain on the JFET have continuity. Seems correct based on this post.

We'll see what Camble says..

Here's my drawing I used (note that DSG on my Fairchild JFETS is ordered differently). Also, I still need to decide which GPIO I'm using instead of 4.

[hueblo]

@hueblo

Hmm... I just built mine (haven't tested it yet), but where you have the wires attached to the switch, I swapped the blue and purple wires. I also swapped the order that the resistor and GPIO4 (and resistor & GND) are connected in the circuit (but I honestly don't know enough about circuits yet to know if that matters).

For me, when the GBZ is off, GPIO24 (I actually used 27 per the first post) & 3.3V have continuity. When the GBZ is on, EN and the drain on the JFET have continuity. Seems correct based on this post.

We'll see what Camble says..

Here's my drawing I used (note that DSG on my Fairchild JFETS is ordered differently). Also, I still need to decide which GPIO I'm using instead of 4.

I based it on that exact post as well, I believe you might be right. Looks like I misunderstood what left pair and right pair of pins meant. I think I was also confused by the post and comparing the diagram from the first post. I just want to make sure I don't break something haha. Also not sure why I listed GPIO24 haha.

[hueblo]

@RxBrad

This better? except for the resistor. I positioned it based on the diagram. I see that in his pictures its before the JFET but not sure if that matters or not.

[RxBrad]

Seems better. I strictly followed the circuit diagram because I wasn't sure if the order the resistor was connected mattered. I'd let someone who actually knows what they're talking about comment on that.

[BigOlTexasBoy]

I went down to my friendly neighborhood electronics repair shop today to pick up the JFET. They didn't have a 2N5460, but had a 2N5461. After looking at the datasheet, there isn't much difference between the two. Here is the link to the datasheet. http://www.onsemi.com/pub_link/Collateral/2N5460-D.PDF
Will this JFET work or do I need to get the specific one on the shopping list?

[Camble]

Sorry guys, I was meaning to draw up a more visual diagram for this. I actually meant to re-write most of the guide to simplify it, since the alternative schematic can be used for both switches.

@hueblo The looks good as far as I can tell.

@RxBrad The physical position of the resistor doesn't matter. As long as it connects to the Gate and Source (ground) pins of the JFET.

@BigOlTexasBoy The 2N5461 or 2N5462 should do just fine. They just have slightly different cutoff voltages, but are all within the range we need.

Remember we have a Discord chat room if you are looking for help. Sometimes it's better than a forum back-and-forth, and you're likely to get a quicker response.