After just a quick look at the circuit, I suspect that the BBB is trying to source/sink too much current?
Also, the BBB has 3.3V logic and you are driving 5V logic. I would suggest that you use an opto-isolator for both isolation and logic level conversion. Bill From: [email protected] [mailto:[email protected]] On Behalf Of Yongfan Men Sent: Wednesday, October 28, 2015 10:58 PM To: BeagleBoard Subject: [beagleboard] Re: My circuit that burnt my BBB needs modify: I wonder if the ground is necessary Forgot to attach the illustration figure. On Wednesday, October 28, 2015 at 10:41:36 PM UTC-4, Yongfan Men wrote: I burnt my BBB, which let me very sad. I ordered a new one online because it's an urgent project, but until I have fully figured out what happened with my circuit, I dare not connect the BBB to it again. This circuit, as shown in the attached image, worked all well during the last whole week. I turned it off this Monday, and turned it on this morning, and Bang! The BBB's burnt. It won't boot up. When I plug the 5V power cable or mini USB cable to it, only the PWR LED will light up a little bit, and it never boots up again. I didn't believe it's my circuit's fault, so I plugged my backup BBB on, and again, it's killed. I burned $100 in 10 minutes. I'm attaching the circuit design here because I need to know if this design is really problematic. Let me explain a little bit: I'm trying to control an I/P converter (SMC ITV0011), which is driven by a 0-5V voltage signal and powered by 12V dc. The problem is It only has three wires, and the ground wire is shared. That's why I think I have to connect all of the ground wires together. I'm using a DAC chip (MCP4725) to generate a proper voltage control signal to the I/P converter. This DAC chip is communicated by I2C, and powered directly by the onboard 3.3V from the BBB. I have carefully checked with multimeter that with digital command through I2C, the voltage could be linearly generated, which is very cool. I'm using a GPIO to control a relay (powered by 5V) to control the on/off of the I/P converter, which means only when I want the I/P converter to be turned on, I will send the GPIO to 1. Otherwise, when GPIO is 0, the I/P converter would not be powered, which is a way of enlarging the lifetime of the $200 I/P converter. That's the whole idea. And I also used a Qt GUI to control the output of both the I2C and GPIO. Last week, I enjoyed a lot using the stylus to drag the slidebar on the touch screen to adjust the pressure output by the I/P Converter. I just don't understand why it suddenly became so dangerous. But last week I did noticed one strange phenomenon. When the relay was not working, there is a strange minus 17 volt on the relay output port. This is probably 12V + 5V, But I don't understand neither why this is a sum nor why it is negative, and since everything works, I didn't pay attention. Today, after I burned the two BBB, I measured the voltage of the relay output port when it's off again. The voltage is 1.7V (5V-3.3V?). So strange! >From my newbie understanding, any output signal should has two wires, one >signal wire, and one ground wire. Because you need a closed circuit to >transfer electrons. That's how coaxial cable works for oscilloscope, and >function generator, and multimeter, and so forth. Therefore I'm connecting the >GND from BBB to DAC, and the GND from DAC to I/P converter; also the GND from >12V dc power source to the I/P converter. This equals that the Ground from the >12V dc power source is directly connected to the BBB. But theoretically, I >don't see any problems, since it's just ground! In the image, I think once I remove the red wire, the BBB will be isolated from the whole 5V and 12V dc circuits. But I don't know if this is the right solution, and also if the voltage output from the DAC will be transfered to the I/P converter. If any of you could explain a little bit about this issue, I would appreciate a lot. Also, If I want to add some more protection to the BBB (on both I2C and GPIO), what should I do? Thanks! -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
