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Old 8th May 2012, 6:31 pm   #1
Vicboduk
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Join Date: Aug 2007
Location: S.W. London, UK.
Posts: 416
Default Studer/Revox Timer Controller

Back in January there was a post asking about timer control of Revox tape machines to record radio programs when out (here). I too had the same problem. A search on the web returned plenty of IR remote control units but nothing with a timer. So I set about creating a solution.
Although I have access to professional design software, PCB production a host of machinery, to keep the project in the spirit of “Home brew” I constructed it at home using basic tools and downloaded software.

The unit is a 1 week, 4 event timer with IR remote control of the five basic functions. Designed predominately to control a Studer A810 but with lead changes (which are automatically detected) can be used on Revox B77 & A77 machines. It is powered either from the machine it is connected to or from the mains. In the latter case a switched mains output is available enabling the controller to power the machine only when needed and to provide a remote On/Off facility. An RGB backlit LCD indicates the current time, mode, which machine is connected and power status. The back light colour can be changed via IR control to suit room décor!

Hardware;
The heart of the timer is a PIC16F877 microcontroller, an old device but it’s what I had to hand.
In fact the only items bought were the case, mains power connector, LC display (I splashed out here and spent a whole pound extra for the RGB backlight! £5-30 from Rapid) and a “One-For-All” remote control from Poundland. Connection to the tape machines is via a 15 way D plug. All other components I had or reclaimed (relays, sockets, etc.) from old projects.

Software;
I made a decision early on that I would write the code in C. My preferred language is assembler where I feel much more comfortable but I force myself to write in C a couple of times a year just to keep my hand in.
Upon reset the unit determines what the power source is and which cable is connected so that the required interface protocol is selected. Four events over a one week period are possible with error checking to make sure I don’t set a stop time before a start time.
I kept the user interface simple (I’ve got to use it!) just four buttons. SET enables the setting of events (genius, eh?) A single press of the DAY, HOUR, or MIN buttons increments the value. A press and hold increments the value at a faster rate. A pending event is shown by its number, else an asterisk is displayed. Different modes are indicated by different backlight colours. Commands sent from the IR remote are decoded, acted upon and indicated on the LCD.

Prototyping;
The initial prototype was a timer only and built on Vero board. It was at this point I decided to add the IR remote function.
After getting the IR working I made the decision to expand the interface to control Revox machines. The B77 presented no problems as it uses an inversion of the logic to the Studer. The A77 however is not totally logic level controlled it requires three sets of contacts, hence the addition of three relays in the final version.

PCB;
The artwork was created with Ares-Lite (web download - not sure if it’s still available). I prefer to hand route I find that auto-routers don’t seem to work too well on single sided boards. I then printed onto a sheet of ordinary A4 paper with a laser printer, exposed for 8 minutes under a 60W UV lamp (4 x 15W lamps in my light box) onto pre-sensitised copper clad (an off-cut from work), developed and etched (more spillages from work) in non-metallic containers all in the kitchen sink. Finally, I sprayed a coat of lacquer on the copper side to stop it oxidising and drilled using a hobby drill. Using this method I’ve always had good results even for boards with small (15 thou) tracks widths.

Construction;
I like my front panels to have no visible screws so I chose a case that had a slot for mounting a board vertically behind the front panel, this would hold the LCD and push switches. The case has four mounting points for the main PCB. I started by drilling and filing the front and back panels. I then made up a template PCB to hold the LCD and push switches to check dimensions. I’m glad I did, the LCD height profile was just greater than the space between font panel and the board! A few strong words later... my solution was to drill six holes to allow clearance for the LCD bezel clips to pass through the PCB this gave just the amount of space I needed - Phew!
I next made up the leads to connect the LCD to the main PCB – This is where I made a really stupid mistake! The connections for the LCD were 180⁰ out. I’d been viewing the LCD connections from the front not the rear, so the lead has a horrible 180⁰ twist in it.
I normally label the front with rub-down lettering and then apply clear lacquer but I haven’t been able to find any of the right size. So, for now I’ve use silver backed labelling tape.

Testing produced no nasty surprises! Just a few tweaks in the software were all that was needed.

Enhancements;
I’m quite pleased with the result but if I were to make another version I would add another two relays. This configuration would then allow for the control of the five basic functions for most machines that have a remote facility irrespective of whether they use logic levels or contacts.

Oops...
Although four events seemed a good idea I’m limited by my tuner not having any pre-set channels.Therefore I can only record from the station I had set it to last! So I now need to modify my tuner to change stations on command.

I feel another project coming on...

Vic


Some pictures;
1; Timer with remote and dual power lead (control lead not shown)
2; Prototyping on a Studer A810
3; Inside PCB
4; Display board showing the clearance holes needed to make it fit!
5; Testing on a Revox B77
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Last edited by Vicboduk; 8th May 2012 at 6:56 pm.
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Old 8th May 2012, 6:36 pm   #2
Vicboduk
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Default Re: Studer/Revox Timer Controller

Some screen shots;

6; RGB back light in all its glory

7; A programming sequence; Yellow, Program mode.
Green, normal timer mode with 1 & 2 events pending, connected to a Studer 810, Tape machine power is off, Timer powered by mains. The plug symbol changes to Tp when the timer is powered from a tape machine.

Red, 1st record event is active.
Final Green, 1st event over, 2nd event still pending.

8; In use on a Studer.
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Old 8th May 2012, 9:44 pm   #3
davegsm82
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Default Re: Studer/Revox Timer Controller

What a fantastic project, well done. I do like the backlight colour changing LCD, it makes me consider something similar for my own project.

How easy was it to implement the IR code? Have you used the common RC6 code?

I'm currently programming an 877 to be a cumulative counter/data recorder which will connect to a geiger counter (or any other event counter).

It works and even communicates with an I2C clock and has a 4x20 char LCD. not got round to data storage yet, but that will be I2C or an SD card.

Dave.
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Old 9th May 2012, 5:37 pm   #4
Vicboduk
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Default Re: Studer/Revox Timer Controller

Hi Dave, thanks for your comments. The compiler I used (Wiz-C) has a RC5 encode and decode library and I had a TSOP IR receiver spare that is why I added the IR functionality. In reality the RC5 decoding had a huge impact on the accuracy of the 24 hour clock function as both libraries share the same timer! I could find no way of re-assigning the timers so I had to tweak other bits of code to improve the clock. In hind sight I should have used a real time clock IC, with back-up power in case of mains power fail, but I didn’t have one to hand...

Good luck with your project. Generally I don’t like using compilers but admit that writing FAT/16/32 routines in assembler would be interesting, required for your SD card if you intend to make it compatible across platforms. So I have to confess compilers and their libraries do have their uses!

Vic
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Old 10th May 2012, 9:02 am   #5
cmjones01
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Default Re: Studer/Revox Timer Controller

That's a very nicely made project, and looks like it should give long, reliable service. I've never seen an RGB backlit LCD module before, but it's a fun idea.

Incidentally, regarding compilers, I used to be distrustful of them for embedded microcontrollers but have over the last 10 years found that the time saved by using a compiler more than outweighs the perceived 'loss of control' from not using assembler. In any case, the amount of Flash memory and CPU power available in modern microcontrollers at a very reasonable price makes it a better deal, for me at least, to complete a project quickly (or at all!) rather than saving every last byte.

Chris
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Old 10th May 2012, 12:48 pm   #6
davegsm82
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Default Re: Studer/Revox Timer Controller

I must admit I've got no faith in cycle-counting clocks like we used to program waaaay back when, this is why I went with the clock IC that i'm using now. Incidentally its a PCF8583 which has an alarm function too, very useful for the sort of thing you've done here. You also get a little bit of eeprom storage on board too.

Have a look here --www.nxp.com/documents/data_sheet/PCF8583.pdf

I use MikroC to do my programming.

Cheers, Dave.
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