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  1. jgauthier

    NOR flash programming

    I am going to implement a microcontroller based on ARM926 that boots from a NOR flash chip. I also want to program that NOR flash chip on board (non-removable). The programmer will power the chip, but while the rest of the circuit is off, I do not want to have the programmer power the rest of...
  2. jgauthier

    Op-Amp voltage follower output different from input

    I am using this op-amp. I have a positive rail (about 10V) and a negative rail (about -13V) explained it in this other post. The op-amp is basically being used a voltage buffer. In my application I have 10 ADC inputs reading current transducers. I am offsetting the current transducer by...
  3. jgauthier

    Using AC/AC wall adapter and converting to DC

    I have a "12VAC" wall adapter. The RMS voltage is really about 9.8V. It's rated at 1000mA. I have a small rectifying circuit to get DC +/- voltage for an op-amp. The negative side of the DC voltage is -13V. The positive side is about 10V. The downstreamdevice seems to pull about 630mA (at...
  4. jgauthier

    Some input/help on this circuit

    Design goals: I have a 9VAC (1A) power supply. I want to power some microprocessor boards with this, as well as monitor it's signal. (the whole scope is larger, but this portion is isolated to the power supply and interactions with it) My plan is to rectify the 9VAC into DC (then use DC/DC...
  5. jgauthier

    Common mode choke - short?

    Hello, I am experiencing weird behavior with a common mode choke and had a few questions. The circuit in question is this: I am using a desktop power supply at 28V and 200mA current. This is the first time I've powered this board. Immediately, the voltage dropped to 0.64, the current went to...
  6. jgauthier

    Help with shunt resistor

    This is most likely an Ohm's law question, but I feel like I need a little help with it. I have this circuit that I use on a low voltage low current system in order to measure the current. My device load is 5V around 3A (peak, not sustained). I'm just looking for some advice on the...
  7. jgauthier

    Multiple GPIOs to direct different voltage to a single device

    I need to create a system where I provide a different voltage to a device given a different GPIO output. Current requirements are not known, but from what I do know about the device it will be very low current. The idea is this: The problem is that there aren't any power multiplexers...
  8. jgauthier

    Multiple isolated devices and GND

    Struggled with the subject. I'll try to explain. I have three devices. I will refer to them as A,B, and C. Device A will power device C. This will happen through a GPIO level trigger, through some relays etc. Device B needs to communicate to/from Device C via TTL level UART comms...
  9. jgauthier

    Looking for a "camera controller" IC

    One of those painful things to me is finding an IC to serve a specific purpose. What I am trying to do: Connect DCMI/MIPI cameras, and "convert" that signal to USB Video Class. Then bundle those together with some kind of USB hub controller into an MCPU. I have a device that does something...
  10. jgauthier

    Determine Sampling

    I have two scenarios, and I am trying to figure out appropriate sampling for these scenarios. First scenario is a piece of equipment with an accelerometer on it. The piece of equipment is going to be activated suddenly and travel at 20ft/s for 21ms. It will also stop suddenly. I want to capture...
  11. jgauthier

    MCPU suggestion

    Hello, I'm looking for an MCPU that can interface with a camera, and wireless. My objective is to grab the video data and send it over the wifi signal. One wifi device I am looking at is the 88W8801 which can be connected using a couple high speed interfaces (USB, SPI). Anyone have...
  12. jgauthier

    Selecting a MOSFET

    Hello, I am having some trouble selecting a MOSFET, and maybe I need more than one. The scenarios is a I have an MCPU that will be switching a GPIO at 3.3V. I originally wanted to switch a MOSFET to actuate a solenoid. The solenoid may be 12V, or it may be 24V. It's not completely decided...
  13. jgauthier

    Looking for a power supply recommendation

    I am looking for a power supply that can provide a high discharge, on par with a LiPO type battery. LiPOs are typically used in quadrotors, and when the motors turn on, especially all 4, they are able to discharge a significant current to power them. Ideally, I'd like a table top DC power supply...
  14. jgauthier

    Noise from DC Power supply

    Hello everyone, At my place of work I have a paging system. The paging system itself basically just accepts audio. So it's powered, and powers the speakers. We've switched phone systems, and the new interface requires a device in the middle that basically connects the phone system to...
  15. jgauthier

    calculate power factor

    This is going to sound like a pretty noob question, and to some degree it is. I'm building a power monitor, and using a current transducer. I read a similar project here:http://openenergymonitor.org/emon/node/58 I went through his code to learn how he calculate power factor, and it makes...
  16. jgauthier

    Building a power monitor

    Greetings, I own a TED (The Energy Detective) 1000 model. It's quite a few years old, and does whole house monitoring. It communicates using PLC. I decided I wanted to build my own, and use a current transformer on each circuit. This would allow me to really see where my power is going...
  17. jgauthier

    Detect ignition from OBD2?

    Hey all, I am working on a project that connects to a vehicles OBD2 connector. The project is in components, and I do not want all of the components to be active when the ignition/engine is off. (To not drain the battery) I'm trying to determine if there is a reliable way to determine...
  18. jgauthier

    Help with MOSFET as a switch

    Hey Everyone, So, I built a circuit and everything was working very well. I was using a MOSFET as a switch. However, I was not happy with my design, because I was "swtching" ground. Effectively, I had two ground busses. One on the drain, and one on the source completely isolated. I...
  19. jgauthier

    LM317L Voltage drop with load

    Hey Everyone, I am struggling with an LM317L (TO-92) which seems to be having a significant voltage drop. Let me set the stage: 12V coming into the circuit, that is then going through a 5V regulator. I have a steady 5V. After that, the rest of the circuit is turned on with a mosfet...
  20. jgauthier

    Sizing a mosfet

    Greetings, A project I have embarked on consists of a micro controller that is "always on". Based on a change, a pin will go low, and that will tell it to turn another pin high. That high pin will then turn on the rest of the circuit. The circuit load could be as high as 2A. I am...
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