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Speaker Power Sequencer via WiFi (In Progress)

Building organ consoles for use with Hauptwerk, adding MIDI to existing consoles, obtaining parts, ...

Speaker Power Sequencer via WiFi (In Progress)

Postby jkinkennon » Mon Nov 06, 2017 10:25 pm

EDIT: For the moment at least I am suggesting that the relays may not be ready for prime time. I got a sticking relay with an LED lamp at 0.3A. May have had a large inrush current. In any case don't follow my lead on this until I find a more reliable board or switch to SSRs.

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I've modified a used Furman RP-8 power conditioner to switch and ultimately to sequence power to my Behringer studio monitors. The original Furman RP-8 has a lot of available space inside. I installed a Raspberry Pi 0w along with a RelayPlate which has seven relays each switching 1A at 120VAC using relays that are rated for 3A. Everything is enclosed in the metal chassis and the relay board is designed to be safe for single point failures.

The relays are controlled by a supplied Python program that sets up a web server on the Raspberry Pi. WiFi access is from a browser on a desktop or tablet/phone. I plan to make some minor changes to the program to allow sequencing the power when a HW organ loads. I'll be learning whether the setup is reliable as I go along, but for now this looks like a nice, dependable setup.

Image

I believe the relays will work fine. If they don't hold up it would be possible to operate larger relays or SSRs from the same board. The ribbon cable is disconnected in the photo. Wiring is 14ga solid copper with soldered terminals. There is one outlet that comes on with the power switch and seven that are remotely controlled.
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Re: Speaker Power Sequencer via WiFi (In Progress)

Postby jkinkennon » Fri Dec 01, 2017 10:35 pm

Since the relays were prone to sticking contacts I exchanged the RelayPlate for qty 4 40A Solid State Relays. With only moderate heat dissipation to the Furman chassis the SSRs will still have adequate capacity in this application. I've designed a simple driver board to piggyback on the Raspberry Pi and sent it off for fabrication. I'll post the schematic and PCB info in a few weeks. Also the Pi program at the same time...
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Re: Speaker Power Sequencer via WiFi

Postby jkinkennon » Tue Dec 12, 2017 9:03 pm

So here's a version that has been working well:

Image

The little purple PCB attaches a driver chip to the Raspberry Pi Zero W which has Wi-Fi built in. I've got a client app that works from another Raspberry Pi so that I know longer have to run across the living room to turn on the speakers one by one. For now I can set and clear any of the four outlet pairs with a single command. As soon as I implement a sequence command and a pushbutton input switch I'll publish the schematic and programs.

The PCB can be ordered here:

https://oshpark.com/shared_projects/FD34YHW9
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Re: Speaker Power Sequencer via WiFi (In Progress)

Postby engrssc » Thu Dec 14, 2017 3:24 pm

jkinkennon wrote:Since the relays were prone to sticking contacts


As in contacts possibly arcing and partially "welding" together? Approx what kind of current were you running thru the relays? I've used similar (blue) relay's rated 110 VAC at 10 amps with no problems - so far. Max amp draw maybe 7 - 8 amps with these relays. These aren't 5 star relays, but their small size is useful at times.

Rgds,
Ed.
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Re: Speaker Power Sequencer via WiFi (In Progress)

Postby joeroberts » Thu Dec 14, 2017 4:18 pm

For those of you who enjoy Gerts many U-tube videos...I thought I would offer this Holiday video featuring one of Hauptwerks instruments.... https://www.youtube.com/watch?v=JVz5Mrl ... ploademail
Happy Holidays,
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Re: Speaker Power Sequencer via WiFi (In Progress)

Postby jkinkennon » Thu Dec 14, 2017 9:16 pm

Ed, the load was a single lamp so the current was under 1A. Rating on these relays was 3A. Just one of the relays was sticking -- the one I was using for testing. I have used quite a number of these:

https://www.sparkfun.com/products/10924

and as part of a kit:

https://www.sparkfun.com/products/13815

I've got these on almost every console I've converted, usually as a part of a relay kit, and have had no issues so I'm not opposed to using conventional relays when they perform as advertised.

Finally got to the bottom of why my project was leaving hanging network sockets today. Now if I get a graphical client app working I'll post a final message here.
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Re: Speaker Power Sequencer via WiFi (In Progress)

Postby engrssc » Thu Dec 14, 2017 9:27 pm

10A on the NC contacts and 20A on the NO contacts at 220VAC

This is a different spec (consideration) I hadn't thought about before.

Rgds,
Ed
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Re: Speaker Power Sequencer via WiFi (In Progress)

Postby engrssc » Sat Jan 13, 2018 5:41 pm

Hi John,

Just wondered if you have noticed any interference using those solid state relays. Got a note from a friend who is using these SSR's to switch power on an effects sound system rack and thinks a lower frequency "frying" sound he hears may be coming from these relays. That rack has much high gain (balanced i/o) gear

Some interesting SSR facts here esp the use of a (protection) Metal Oxide Varistor (MOV) across the output connection:

https://www.phidgets.com/docs/Solid_State_Relay_Primer

Rgds,
Ed
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Re: Speaker Power Sequencer via WiFi (In Progress)

Postby jkinkennon » Sun Jan 14, 2018 3:42 pm

I have used three models of SSRs in organ consoles and have never heard any noise from them. Attention does need to be paid to providing sufficient heat sinking. For this application the currents are low, the SSRs are overrated, and the Furman chassis doesn't even get warm. When I've used SSRs to power PA amps I've mounted them on appropriate (large) heat sinks.

Regarding the project, I've been unhappy with the Raspberry Pi Zero needing restarted once and "losing" a fix which kept the WiFi from going into a power saving mode and becoming slow to respond. I may replace it with a PIC32 board which has WiFi and may prove more reliable.
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