Trying to make a 64-bit Switch - Page 1
Forum section: electronics / beginners

author: cmckilla44
author_rank: Contributor
timestamp: June 15, 2017, 04:06:07 pm
content: Hello all,I am new to this forum. At the moment, I am a student as well, so I am a noob at electronics and electrical engineering... But I am trying to solve a problem. What I need is a 64-way switch that can activate the power buttons of old servers I got.What I have come up with so far is this. I am using a Raspberry Pi as the microcontroller. I use the Pi to control two shift registers, which each have 8 outputs. That gives me 16 outputs that I can control, each with a high or low voltage.Next, I am using multiplexing to control 64 outputs; 8x8=64. So, one shift register controls 8 rows, while the other controls 8 columns, to give me 64 different possible outputs.Finally, to "press" the power button on the server, a circuit needs to be closed so that current will flow from the + to the - of the power button. My initial idea was to use an Optoisolator, which is a simple chip that closes a switch when the other side's LED is turned on. At first, I tried using one Optoisolator to activate the power button, but the current flow must be bidirectional. Thus, I use two opto-isolators connected to eachother with opposite output pins connected together, and that will activate the power button of the server.Thus, my requirements are two shift registers, 64x2=128 Optoisolators, and a raspberry pi, to control 64 different switches.Is there a better way to do what I am trying to do? Or is there a way that my method could be improved? Would love to hear from you guys. Thanks!!Clay

author: Zero999
author_rank: Super Contributor
timestamp: June 15, 2017, 05:51:07 pm
content: It's possible the opto-isolator doesn't need to be bipolar. The first time you tried it, it probably didn't work because the polarity was incorrect and if you had reversed it, it would have worked.

author: cmckilla44
author_rank: Contributor
timestamp: June 15, 2017, 06:35:15 pm
content: You know what, you are exactly right. So I will use one if i dont need bipolarity in my switch. Thanks for that!Clay

author: dave_k
author_rank: Frequent Contributor
timestamp: June 15, 2017, 06:48:36 pm
content: Quote from: cmckilla44 on June 15, 2017, 04:06:07 pmWake On Lan ... ?

author: theatrus
author_rank: Frequent Contributor
timestamp: June 16, 2017, 06:27:44 am
content: Quote from: dave_k on June 15, 2017, 06:48:36 pmIPMI

author: X
author_rank: Regular Contributor
timestamp: June 16, 2017, 06:57:59 am
content: A cross-bar setup might work better for your situation. If you hold the power button for too long by latching the output, you will reset your server after a few seconds.Optocouplers can achieve the result you want, but you need to find out what the switch is shorting out, and set the optocoupler that way. You don't need two in parallel.

author: cmckilla44
author_rank: Contributor
timestamp: June 26, 2017, 05:33:28 pm
content: Thank you all for your replies! I was able to figure it out. I will be using two optocouplers per switch so that the switch is bidirectional, even though I could have used one. Thanks again to all of you who took the time to reply, hope this thread is useful to others as well!