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  1. gorgon

    Component questions (transistor, capacitor)

    You need to take care when using a PNP transistor driven from a lower voltage, using a resistor divider that will turn off the PNP properly when the driving signal is 3.3V(high) You should also check that the output is 5V compatible, so it doesn't burn out due to overvoltage. If the output...
  2. gorgon

    Trouble with tribbles.. erm, timers.

    Just a comment on the driver structure of the matrix. You use ULN2803 to sink the columns, and the 74HC595 to source one LED. That is a bit on the low side, if you want some light out of the LEDs. You will need to make a source driver. A 74hc595 will only source(and sink) around 6mA, and still...
  3. gorgon

    O-Scope Ext. Trigger used for?

    More advanced scopes like the TEK2221a also allow pre/mid/post-triggering so you can see what happend before and/or after the trigger activated. The mid- and post-triggering is very useful when you debug code in microprocessor circuits. You can trigger on an activation signal in a piece of...
  4. gorgon

    micro controller design

    Your address space and address pointers are not consistent. from the amount of 64k blocks, you would need at least 18bit address pointers, maybe more. A 64k stack makes it possible to live on it, at least compared with the rest of the specs.
  5. gorgon

    LED Project help needed

    You could try to increase C1 to a higher value.
  6. gorgon

    O-Scope Ext. Trigger used for?

    The external trigger is normally used when you want to trigger on a signal you are not looking at on your normal input channels. Any signal that is inside the electrical spcifications of the external trigger input can be used as a trigger source. There is no fixed rule for what you can use...
  7. gorgon

    USB to serial question

    It depends on many things. First of all how many boards you need to make and how good you are at making PCBs.
  8. gorgon

    USB to serial question

    0805 is ok to handsolder, so is 0603, but for smaler sizes you more or less need to reflow solder it. Transistors in SOT23 is also ok to hand solder.
  9. gorgon

    USB to serial question

    You can always make it smaller, using SMD components, but it comes down to cost. If you plan to produce a great number of these, you may think of making a small PCB as a part of the plug into the Cobro, then you only need to attach the wires from the USB Device to this PCB and heatshrink it...
  10. gorgon

    USB to serial question

    This is related to a standard RS232 port on the PC. You wanted to use the USB Device, and you can't use the opamp solution for this. If you are using the 2 transistor Circuit I sketched for you, the main question is, does it work as intended? Does it disable the Power save, as explained...
  11. gorgon

    Connecting two battery pack in parallel with a MOSFET

    Here is a Controller for the ID function: http://datasheets.maximintegrated.com/en/ds/MAX16914-MAX16915.pdf just add the MOSFETs. Due to the problem With the body diodes, the OPs variant is only half a Ideal Diode in function.
  12. gorgon

    Connecting two battery pack in parallel with a MOSFET

    A normal blocking 2-MOSFET switch use two P-channel OR two N-channel MOSFETS connected Source to Source. To switch in the +V lead you either need two PMOSFETs, and activating the gates to 0V, or you use two NMOSFETs With an extra >+V Vgs Power solution. This is normally a charge pump solution...
  13. gorgon

    about dc ckt. ground

    The photos doesn't tell too much. Could you please post a schematics of the two circuits?
  14. gorgon

    about dc ckt. ground

    If you are feeding both circuits from the same power supply, and the Power short circuit when connecting the GND of both circuits, it could indicate that GND for one circuit is +Vcc for the other. Or something else is not connected correct.
  15. gorgon

    Connecting two battery pack in parallel with a MOSFET

    Yes, that was the idea, but as usual I lacked the detail. Thanks Steve :)
  16. gorgon

    Connecting two battery pack in parallel with a MOSFET

    You should be aware of the fact that you 'ideal diode' is just another NMOSFET with a control circuit included. Since you have no control over the function of this 'diode' there is can be a risk of shorting the batteries together, With the extreme currents that can be the result. Before you...
  17. gorgon

    LM393 comparator...

    You should be aware that the input common mode range is 0V to Vcc-1.5V or 0 - 1.8V if your supply is 3.3V. If your inputs get above this value things can happen inside the chip. I've seen LM339 letting out the magic smoke, putting enough current into the inputs at these levels close to the Vcc...
  18. gorgon

    Current Direction

    Well it looks that my selection of the sole word 'defined' might have been a bit bombastic, and I stand at least partly corrected. ;) From Wiki: 'A flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the...
  19. gorgon

    Current Direction

    Just a little comment. The Arrows in Your drawings are not showing the current flow, but the Electron flow. This is defined to be -I or negative current. The current I is defined to flow from V+ to V- of the battery. This is important to get correct when you start setting polarity on the...
  20. gorgon

    Using a voltage converter...

    Please note that there are different plugs in many countries. The UK plugs are big, and very different from the plugs used by other countries in Europe. Many modern wallwarts span the voltage from 100V, to 240V, both 50 and 60 Hz. If you have those you are safe. The 50/60Hz problem is...
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