The circuit looks reasonable in general, but it's hard to tell because you don't show all the connections and labels. Like, what are the G and V things on the relay boards? I assume you're talking about http://www.superdroidrobots.com/product_info/TE-249-070_Schematic.pdf, so probably JP17-1 and -2, but how would we know for sure? can you redraw your schematic with more specific connection diagram, listing the specific connections you make to the relay board and the DAC?
Also, it's possible to mess up by plugging the things in the wrong sequence, e.g. if you work under power and connect the data lines before connecting power. On Wed, Oct 28, 2015 at 10:57 PM, Yongfan Men <[email protected]> wrote: > 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.
