Wireless Relay-based Guitar Effects Switcher

[Chico]

I just added a draft writeup that addresses how I implemented Wireless Communication in my ASMOP inpsired relay switcher.

It is still a work in progress, so comments, corrections, suggestions and criticisms are all welcome.

See //www.circuitmuse.com

For those who like reading Assembly language, I also included at the end of the article, the AVR code that implements my software UART.  As the article suggests, a software based UART was one feature that I found to be key in maintaining long term synchronization.  (If any of you have had success using a hardware UART with wireless RF chips, please let me know how you did it).

I have an outdoor gig this weekend, and that should prove to be a good next step in testing the reliability of the unit.  However, indoors, operation has been smooth and reliable (as he knocks on wood).

Best regards

Tom

[Hal]

have i mentioned that you're my hero?

I think i did, put I will again.

[R.G.]

Good, solid DIY engineering work there.  

I especially like the work on the synchronizing the RF transmissions.

A couple of other questions for things I didn't see that I may just have overlooked in reading:

Did you by chance include an LED that indicates "RF signal received and in sync"? That would tell the player when he's too far away, has interference, etc., that the RF link won't work. The standing sync operation is there, just needs an indicator.

Did you by chance include an option for a hard wired link, say a 25' telephone wire with RJ11's on it so that in high interference environments you could do the same discipline by wire? One of the sets of wires could disable the RF link and patch in the wired link, as well as powering the remote. Useful for guys who have to make their living playing guitar.

[Chico]

RG:

Currently, I use a 2 digit seven segment LED for the Receiver display.  It is a LUMEX LDD C814 RI that I picked up from Mouser.  Each digit includes a "period" or dot in addition to the seven segment LEDs.  I use the dot after the BANK to indicate synchronization.  When the Receiver Syncs to the Transmitter, this dot lights up.  If for some reason the sync code is lost, then the light goes out.

The second dot (after the PATCH LED) indicates that the system is in programming mode when lit.  In programming mode, the BANK PATCH and store functions on the panel of the receiver are enabled.

This can be a clutch go-to if the transmitter dies.  Just turn the Receiver to program mode, and manually scroll through the patches.  Not gratifying, but a workaround.

I also included a wired connection as a backup.  Basically, the transmitter output is coupled to both the RF transmitter and to an RS232 driver chip, the MAX232.  

There is a complimentary MAX232 in the receiver.  
On the web site, the first page that includes photos of the prototype shows a photo of the back panel.  Right next to the power switch are two jacks.  The top is for a wired connection to the transmitter labeled PEDAL (in hindsight, that label is probably not the best choice), and just below that is a jack for the antenna.

Right now, the wired connection does not transmit power.  Great idea though.  My initial thought was that I always gig with an extra cord, so why not just use a guitar cable.  In my testing, this has worked out ok.  The use of the MAX232 driver chip stemmed from the fact that I had several in my spare parts bin.  When I started getting into AVR, I stocked up on parts that I though may come in handy, and this was one of them.

Also, it may be peculiar to use 1/4 jack for an antenna input.  The antenna to the RF chips is just a 30cm strand of wire.  Well, the short answer is that I bought a bunch of 1/4 jacks for this project and had a box of old patch cords.  It was short work to use the jack from an old patch cord to make an antenna that can be easily plugged into the unit.

Best regards

Tom

[bond]

sites dead

[Chico]

Yea, sorry.  I decided to change providers and have been slow at getting the new site up and running.  If anyone wants the documents from the site, they can PM me and I will email them to you. 

Look for the site to be back up in the next few months.

Best regards

Tom