• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Cybernetic Data Products LED sign PS help please

slywuf

New Member
I recently came across a couple of old LED signs made back around 1990 by Cybernetic Data Products. These went by the name "Silent Radio." Unfortunately, the ones I have did not come with the power supply module. I think earlier models had the complete power supply built in and you just plugged in a standard AC cord to power it up, but mine have a 5 pin DIN connector on the back instead. I took the circuit boards out of the case and found that 5 pin DIN connector mounted on a circuit board that appears to be the power interface for the rest of the sign.

I made a schematic drawing of this board in order to figure out what voltages are needed at the 5 pin DIN connector in order to bring the sign to life.
I'm pretty sure the drawing is accurate, but I'm not understanding all that I am seeing there.

PS interface.jpg


So - in the upper left of the drawing is P1, the 5 pin DIN where power comes in. On the right is a 5 pin connector that connects to the remainder of the LED sign. The TL072 op amp specs say that VCC is normally +/- 15 volts, so looks like pin 2 on P1 should be -15 volts and pin 4 of P1 should be +15 volts.
Pin 4 of P1 also connects to the input of a 5 volt voltage regulator, so that 5 volt output appears on pin 5 of P2. Pin 1 and 3 of P1 are ground, so that just leaves pin 5 to figure out. I don't really see what is going on with the two op amps and the TIP121 power transistor. Can someone help me figure this out so I can build an appropriate power supply to feed P1 please? Many thanks in advance!
 

slywuf

New Member
All power for the LED sign enters through the 5 pin DIN connector. Looking closer at the main board that this regulator board plugs into -
Pin 1 from the P2 connector connects to the drain of seven power MOSFETs - type IRFZ34. These MOSFETs are probably the column drivers for the (29) 5x7 LED modules. Guessing they need 9 - 12 volts to operate, so pin 5 of the P1 (DIN connector) needs to have
that 9-12 volts applied. Looks like the TIP121 will act as a shunt regulator for that voltage. Soon, I will try firing this sign up by putting +12v on pin 4 of P1, -12v on pin 2 of P1 and I'll put a variable power supply on pin 5 of P1, start at around 6v and go up a few volts while observing any life coming from the LED display. See anything wrong with that approach?
 

AnalogKid

Well-Known Member
Most Helpful Member
The image is not clear - what is the value of R1?

Pin 1 - GND
Pin 2 - V- for the opamp
Pin 3 - GND
Pin 4 - V+ for everything
Pin 5 - ???

Because of the large value (not clear) of the capacitor and the connection to a power transistor collector, pin 5 probably is the main power for the LEDs. Are R10? and R13? both connected to GND near the TIP121 emitter?

ak
 

NsrMagazin

Member
You can use a variable power supply to test it, start with "5VDC/ 0.5ADC" and keep increasing the voltage until you reach 12 not more. Then try again from 5 to 12 but with "1ADC" and so on.

Maybe it will be better to use "8VDC" as the upper border and "1ADC", its up to you since you are risking. Do it at your own risk!
 

slywuf

New Member
Yes - R10 and R13 are connected to ground, along with the TIP121 emitter. R1 is a power resistor .01 ohm, probably about 2-3 watt.
Agreed - pin 5 on the P1 connector will supply power to the (7) IRFZ34 power MOSFET transistors (on main board) to drive the LED columns.
Waiting for a power supply to show up that will provide the +/- 12v for pins 2&4 on the DIN, and I will be able to test this.
 

slywuf

New Member
Update on the LED sign project -

Just got in a power supply that has a +/- 12v output, so hooked that up to the P1 connector pins 2 & 4. Put a variable voltage power supply on pin 5 of P1 and set it to 5V. Turned on the power and got no life from the LED display at all. Monitored the voltage output on P2 pin 1, which looks to be the voltage being applied to the 7 column drivers of the LED display. It was showing just a little less than 5 volts at that point. I slowly turned up the voltage going into P1 pin 5 and it continued to increase until it got to 5.6 volts and then would not increase further. Appears that the TIP121 regulator is holding it at that voltage. Voltage going into the TL072 op amp was good at +/- 12v. The LM2940 regulator was doing its job - good output at 5 volts. Maybe something else on the main board with all the logic is kaput... I dont know. I have one more of these signs that I will apply power to tomorrow. I suppose if all else fails, I can try driving the LED matrix displays with an Arduino, but I have no experience in that area. Thoughts?
 

NsrMagazin

Member
Its not a good idea if you don't have experience. But its not impossible either, give us the display model and a picture please and we can help you.
 

slywuf

New Member
The 5x7 LED matrix display is a LTP2157AE. There are 29 of them. Columns connect to DS75492N drivers and GD4015B shift registers.
Rows connect to IRFZ34 power MOSFETs. I'd like to be able to use RSS feeds to apply to the adruino and have that drive the LED array. However, I dont know what is required to make that happen.
 

MichaelaJoy

Active Member
Here's the datasheet for the display module.
https://www.alldatasheet.com/view.jsp?Searchword=LTP-2157AE

And the datasheet for the 'CD4015b'
http://www.ti.com/product/CD4015B

You'll need to create or get a full schematic, because it looks like something is needed to clock data into the display. (Maybe a serial interface of some kind?)

Is there a missing module that this display plugs into, like a character generator?

If so, then your Arduino has to imitate that, and send data to the display for you. :)
 

slywuf

New Member
Yes, I've seen the data sheets for the components in the LED display and power supply regulator. There is no schematic available for this SilentRadio sign - I've looked extensively... these were made back in the late 80's. Attached to the LED array board is the main logic board. As stated above, I was not able to get any life out of the LED array when I connected DC power to the regulator board, and assume that there is a problem somewhere on that main logic board. It uses a 6502 microprocessor. Here is what that board looks like:

mainboard1.JPG



The power supply regulator board (schematic at the beginning of this thread) plugs into the white 5 pin connector on the right of the picture. The board underneath the logic board is about 40 inches long and contains the 29 LED matrix arrays.

There are 12 leads that connect the logic board to the LED display board as follows:

1. 5 Volts
2. Ground
3. Seven common Anode lines (5 volts to light up)
4. Seven common Anode lines (5 volts to light up)
5. Seven common Anode lines (5 volts to light up)
6. Seven common Anode lines (5 volts to light up)
7. Seven common Anode lines (5 volts to light up)
8. Seven common Anode lines (5 volts to light up)
9. Seven common Anode lines (5 volts to light up)
10. Ground
11. Data
12. Clock

Where I am at a loss is coming up with an arduino that will replace the main logic board and interface the 12 pins shown above.
 

NsrMagazin

Member
I don't know anything about this processor "6502". Testing the 3 components(regulator, logic board and LEDs) is almost finished. You know the regulator is ok, now you need to check if the logic or LEDs are damaged.

To do this you do not need the specific values for the LEDs, you can just send random values. Some of the LEDs should be light.
 

MichaelaJoy

Active Member
slywuf: I hope you have a decent scope. Without it, you're flying blind.

Here's some info on the 6502
https://en.wikipedia.org/wiki/MOS_Technology_6502

and resources.

http://6502.org/

Can you take a better picture? More detail on the TTL around the CPU is needed.

Notice the empty socket next to what looks like a RAM chip? It's probably for an EPROM (maybe 2716, or 2732, but it could be a 2764)

The EPROM holds the message that's displayed.
Look here:
https://en.wikipedia.org/wiki/EPROM

You want to take a look at those 7 drive lines and see if they're mutually exclusive (think of the 74AC138)
If so, the CPU is sending the data out, one scan line at a time and latching it in those shift registers.
Then, those anode driver lines will toggle through the anodes and light up the leds.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
I don't know anything about this processor "6502".
The 6502 was one of the most popular processors there was, it was used in countless computers and development systems, including the Commodore PET, the Apple 1, the Commodore 64 etc.

Like many people, it was the processor in my first computer.
 

rjenkinsgb

Active Member
Notice the empty socket next to what looks like a RAM chip? It's probably for an EPROM (maybe 2716, or 2732, but it could be a 2764)

The EPROM holds the message that's displayed.
... Or, the EPROM held the actual control program for the sign, and the message was just stored in battery backed RAM to make it easily reprogrammable; there looks to be a big backup battery, the lump with the Panasonic label.

If that is the case, then without its program, the control board is scrap (or salvage, anyway).
 

NsrMagazin

Member
I started with Motorola HC11, but that does not means I know all old processors.

It would be good if we can confirm which of the 3 blocks is damaged and then figure out how to replace it.
 

slywuf

New Member
OK, thanks for all the comments and suggestions. I really dont think it would be worth trying to fix the logic board for this sign. At best, you could type out a message on the Cybernetics Data Products keyboard and have it display. I would like to increase the functionality of this sign by being able to supply various RSS feeds thru an arduino to drive the existing LED matrix on the 3 foot long display board.

I just finished putting together a drawing that shows the 5x7 LED matrix, Hex digit drivers, and shift register:


matrix driver.jpg


On the left side of the drawing, there is a list of the traces (1-12) that run the length of the 3 foot display PCB.
My question is - how can that buss be connected to an arduino in order to drive the (29) 5x7 LED matrix units?
 

unclejed613

Well-Known Member
Most Helpful Member

NsrMagazin

Member
You need 12 pins for both sides(5+7). You can remove the hex driver and shift register, because Arduino can supply 40mA per pin. You activate the power supply on 1 of the lines and make an input 1 of the columns. I will find the code later as I am going to get a few documents.
 

Latest threads

EE World Online Articles

Loading

 
Top