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16  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 23, 2012, 08:05:50 pm
Does the relay control have a ground that goes from arduino to breadboard then to relay control? Just checking.

The 5V relay control is currently powered by the same 5V/GND from the Arduino to the LCD & backlight. Is this correct?

About half an hour ago, the garbage character problem showed up again. It happened when I tried to turn on and off 17 solenoids (one by one in consecutive order with one second in between). But it did not happen again when I repeated the same steps. So the problem is evasive. BTW, I do not have the 10uF cap between Vcc and GND yet as I still need to get the part from the local store.
17  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 23, 2012, 12:06:22 pm
Hi dc42 and liudr,

Thank you for your advice. Attached is a closeup of the Arduino with labels. It should clear up some confusion regarding the wiring.

@liudr, I will add the cap between Vcc and GND.

@dc42, just to confirm, the Arduino, LCD and backlight should be powered as follows:

Arduino <- dedicated 12V power supply
LCD <- dedicated 5V power supply
backlight <- same power supply as the LCD

Many thanks!
18  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 22, 2012, 06:49:02 pm
OK got it. If you only switch relays without solenoids attached, will you see garbage on LCD? Can you give a large picture of the arduino and LCD included?

Sorry for the delay. This past week I have been trying to find a consistent way to reproduce the problem. I cleaned up the wiring, so I can take a better picture to show you guys. After that, I have not been able to reproduce the problems consistently (the problem still exists). Attached are the photos of the Arduino side with two closeup photos. The wiring of the LCD is the same as the Arduino tutorial, except I have added a 150 ohm resistor to the LCD backlight supply voltage as suggested by another post. I will add more labels to the wiring later tonight or tomorrow, so you guys can better understand my setup. Thanks.
19  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 15, 2012, 01:43:49 am
Help me here, is this what you want to do?

Turn on a relay that powers a solenoid? The diode needs to be at the relay coil side. The solenoid? separate the 12V supply ground from arduino's. They don't have to and should not share grounds.

I only see the box (you held it in your hand in the other picture). Is the relay inside the box or is it outside your picture?

Yes, there is also a diode on the relay coil side. Attached are the schematics of the customized 8-unit relay board and a photo of the relay PCB. I am using the Arduino to control the two input pins of each relay (a matrix configuration), so I can control 256 relays with one Arduino. The box in my hand is the solenoid. The relay is shown in this attachment.

Regarding the ground, Arduino is powered by its own 12V power supply, which is separate from the 12V power supply for the solenoid. The relay is 5V and is powered from Arduino. Thanks.
20  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 14, 2012, 01:53:36 am
If you get problem when you disengage the solenoid, then it is the diode's problem or how it is connected. If you have it correctly connected then the diode will bypass the back EMF. Let us see the connection diagram and the actual photo.

Attached is a photo of the relay and solenoid. I was trying out different length of the wires, and it seems that a long wire between NO of the relay to the cathode of the diode yields the best result (even though it still does not completely suppress the back EMF). The power supply is a dedicated 12V with 10A rating, and has no connection to the Arduino UNO. The 12V solenoid draws about 1A when active. Please let me know if you have any suggestion or need more information. Thanks.
21  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 13, 2012, 11:51:09 am
Yes, it does seem strange. I suggest you test the diode that you fitted in the new position. Does the garbage appear when the solenoid turns on, or when it turns off? Also see my previous reply about +5v and ground wires to the LCD. A photo of your wiring would help.

I will do more testing here, and take a photo after I clean up the wiring. The garbage characters appear always when the solenoid is turned off. I am powering the LCD using the 5V and GND pins directly from the Arduino UNO's power rail. Thanks.
22  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 13, 2012, 01:07:52 am
From the photo, it looks as if those solenoids are held together by 4 screws with hex or Torx heads. It might be worth disassembling one, to see whether there is room to fit a diode inside (although that will probably invalidate the warranty). If space is limited, then depending on the current taken by the solenoid, you may be able to use a smaller diode. You can also get 1N400x diodes in SMD packages.

@DC42, I opened up the solenoid, and inside is one complete unit, so there is no way to place the diode inside. What I did was to place the diode as shown in my previous photo (where the scissors symbol is pointing at) to see if I can completely suppress the EMF. To my surprise, this new setup actually made it worse. Now I see garbage on the LCD all the time. Attached is a drawing of my old and new setup. The diode on the left-hand side is the old setup where I place the diode about half way between the solenoid and the 12V power supply. This setup works sometimes. The diode on the right-hand side is the new setup, which always fails, i.e. garbage on LCD. This is completely opposite to what I expect to happen. Any suggestion? Thanks.
23  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 11, 2012, 01:17:51 pm
Thanks a lot, mate! Placing the diode across the solenoid did the trick! It's much more stable now. I think I just need to place the diode even closer to the solenoid to completely get rid off the problem. Right now the diode is about 30cm away from the solenoid.

I have another similar circuit with a LCD and 256 relays (to control 256 electronic solenoids). This setup also experiences the same rubbish character problem on the LCD, so I will need to place the diode across all the solenoids as shown in the attachment. Is there an easier way to place the diodes? It's quite a bit of work to cut the wires and solder the diodes on all 256 solenoids. Thanks again!
24  Using Arduino / Displays / Re: Problem with LCD and Motor on: October 11, 2012, 01:03:43 am
I am having similar issue. My LCD connected to the UNO displays strange characters after turning on/off the 5V relay for a dozen times. The relay controls a 12V solenoid (an electric strike for a door). I know it has to do with the EMF because if I disconnect the solenoid, the problem does not happen. My relay setup is similar to this: http://www.instructables.com/id/Connecting-a-12V-Relay-to-Arduino, except my relay is 5V, and I am powering the relay with 5V from the UNO. Here are the things I have tried so far:

- used an external power adaptor to power the 5V relay
- placed 6.8uF cap across the coil of the relay
- placed 90uF cap across the 12V rail
- used a separate 12V power supply for the solenoid

Does anyone have any suggestion for me to how suppress the EMF? Thanks.
25  Using Arduino / Motors, Mechanics, and Power / Re: Urgent help needed - relay with load resetting Arduino on: September 06, 2012, 01:39:17 pm
Yes, OE is tied to ground, and MR is set to high.  The serial port is connected to pin 0 and 1 on the Arduino and to the PC.

At any time, only one relay will be enabled, so two transistors and one LED. I can remove the LED to see if it helps. Please keep sending any suggestions you may have, and I will give it a try. I am desperate here. Thanks.
26  Using Arduino / Motors, Mechanics, and Power / Re: Urgent help needed - relay with load resetting Arduino on: September 06, 2012, 11:05:45 am
Sorry, it's SN74HC595N, 8-bit shift register. http://www.ti.com/lit/ds/symlink/sn74hc595.pdf
27  Using Arduino / Motors, Mechanics, and Power / Re: Urgent help needed - relay with load resetting Arduino on: September 06, 2012, 03:33:36 am
After spending the past six hours debugging, I think I may have narrowed down the culprit. I don't have 0.1uF cap in hand, so I used 0.33uF cap across Vcc and GND at pin 4 of the relay. The problem still persists. Then I stripped down my code, removed the Ethernet shield, and just have a command-line turning on/off a specific relay. That's when I found out that the culprit may be the shift register matrix I am using to control the relays. Attached is the schematic of the shift register matrix, which consists of two shift registers for the 16-bit row and two shift registers for the 16-bit column. If I connect the solenoid to the relay, all 16 row LED's on the shift register matrix are turned on after the relay is turned off. So I added 0.33uF across the Vcc and GND on all four shift register IC's, and added a pull-down resistor on the latch pin of all four shift registers. Now instead of all 16 row LED's turning on when the relay is turned off, the serial port receiving stops working (I can still type to turn on/off the relay). So it is more stable now, but still some interference.

Any suggestion on what to try next? Thanks.
28  Using Arduino / Motors, Mechanics, and Power / Re: Urgent help needed - relay with load resetting Arduino on: September 05, 2012, 06:22:04 pm
Yes, it's a LED.

Will try the cap tonight and report back. Just to confirm, do I pop 10uF caps or 0.1uF caps at pin 4 to ground? Thanks.
29  Using Arduino / Motors, Mechanics, and Power / Re: Urgent help needed - relay with load resetting Arduino on: September 05, 2012, 05:52:07 pm
Good observation on the diode to pin 5. It was a mistake in that layout revision, and was corrected by hand soldering on the PCB. Regarding the extra diode to the collector, it is solely for visual notification, so we know which row/column matrix is turned on. Thanks.
30  Using Arduino / Motors, Mechanics, and Power / Re: Urgent help needed - relay with load resetting Arduino on: September 05, 2012, 03:54:30 pm
Thanks for the quick reply. Attached is the schematic for the customized 8-relay circuit. Each relay requires two inputs from the Arduino (I am using shift registers to make a row-column matrix to control 256 lockers). Below is the datasheet for the relay.

http://www.punchlight.com/files/relayLEG-5_datasheet.pdf?PHPSESSID=b74e7ea0c06bd20c0a795c669e2ca461

Everything works, except when the solenoid is connected to the relay (connector J) and is switched on and then off - that's when Arduino is reset..
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