Search results

Search Forums New Posts
  1. KrisBlueNZ

    0.5 volt signal to earth signal

    V2 and V3 are voltage sources that are used to generate an input signal for the simulation. One generates the triangle wave - a steady rise and fall, and the other generates the noise that appears as wiggles on the Vin trace (green). These aren't part of what you need to build; they just...
  2. KrisBlueNZ

    Designing DC motor with 8051 and transisors

    Yes, as kpatz says, the difference is in how the transistors are used. In the first circuit, all four transistors are NPNs, and are turned ON by positive bias on their bases. Remember that in an H-bridge, current flows in a down-across-down pattern. So in the first circuit, current can flow...
  3. KrisBlueNZ

    What is this part called?

    I can't make out anything more than a black rectangle. See if you can get some better pictures.
  4. KrisBlueNZ

    What do different color wire mean?

    I think the person who drew up that wiring diagram just used different colours for the wires so you could follow them easily on the diagram. You can use different colours if you want - the colour of the insulation doesn't affect the behaviour of the wire, obviously. But if you use the same...
  5. KrisBlueNZ

    Help please

    The heater current doesn't flow through the board, so I don't think that's a likely explanation, but I agree there is probably something causing the boards to fail. I think the first step is to find out how the board has failed, then investigate what could have caused that failure.
  6. KrisBlueNZ

    What are these?

    Yes they're multi-layer ceramic capacitors (MLCCs) in SMT (surface mount technology) packages. They don't normally have markings.
  7. KrisBlueNZ

    0.5 volt signal to earth signal

    Sorry for the delay! I hope this will still be useful. Here's the design I've come up with. It seems to work OK in simulation. You may need to adjust it once you've built it up, to accommodate component variations. I will explain this below. The circuit uses three transistors, and some...
  8. KrisBlueNZ

    Find MOSFET equivalent

    All of those four MOSFETs I suggested are equal to, or better than, the original device for the main specifications (maximum voltage, maximum current, etc) but there are other specifications that relate to switching behaviour that I don't know much about. That's why I have identified those...
  9. KrisBlueNZ

    Find MOSFET equivalent

    I think this might be one for Steve. I found a data sheet and have attached it to this post. The basic information on the device is: STP7NB80FP: STMicroelectronics N-channel "PowerMESH" MOSFET in TO-220FP (full plastic enclosed package) Vdss(max): 800V Id(max): 6.5A Id (pulsed): 26A Ptot at...
  10. KrisBlueNZ

    Project - Conveyor system using 555's

    An N-channel MOSFET connected in place of the transistor, with gate=base, drain=collector and source=emitter, will behave similarly to an NPN transistor. When the gate is driven positive, the MOSFET will conduct current through its drain-source path and the load will be energised. The main...
  11. KrisBlueNZ

    Project - Conveyor system using 555's

    RT1 isn't used for biasing. It's in series with the motor. You said the circuit can switch up to 5A. Not 600 mA. Not without providing a lot more base current. The minimum current gain for a BD139 is only 40. That's why I suggest using an N-channel MOSFET.
  12. KrisBlueNZ

    Help please

    If you read the whole thread, you would know that the problem is on the circuit board. He has had to replace it seven times and each time, that fixed the problem.
  13. KrisBlueNZ

    Remote Control Circuit with CD4017 - counter decoder

    That's not ideal because the LED is supposed to be driven at about 33% duty cycle. When you divide 455 kHz by 12, the Q4 output is low for 8 out of 12 cycles, then high for 4 out of 12 cycles. This is a duty cycle of 33% which is what you want. But if you divide 4.9152 MHz by 130, you will get...
  14. KrisBlueNZ

    Connecting 12v dc motor to a rc circuit car

    Yes! If the original circuit was designed to drive a less powerful motor, and the new motors you have need 8A each, you'll need to make some changes to the drive circuit. Start by posting details of brands, model number etc for the RC receiver and the motors, and upload some photos of both. See...
  15. KrisBlueNZ

    Hey from the frozen tundra...Minnesota!

    Hi Brandon and welcome to the Electronics Point forums :-) Thanks for introducing yourself. I hope you enjoy it here.
  16. KrisBlueNZ

    Remote Control Circuit with CD4017 - counter decoder

    That's good news! You can use a 7805 or 78L05 but you'll need at least one more cell in the battery. 1.5V x 4 = 6V which leaves only 1V across the regulator. That's OK for a "low dropout" regulator, but it's not enough "dropout voltage" for a 78x05. 1.5V x 5 = 7.5V which leaves 2.5V dropout...
  17. KrisBlueNZ

    Voltage converter 120V to 220V

    That won't work in this case because (it appears) there is a transformer AND a switching power supply. Increasing the rated voltage of the capacitor in the switching supply won't work; the primary side circuitry will all be designed to run from 110V and will most likely pop its clogs if driven...
  18. KrisBlueNZ

    What do different color wire mean?

    There are no rules about wire colours, only conventions. The simplest rule is "black is negative, red is positive". Black is normally used for the 0V ("zero volt") rail of a device. Almost every non-trivial circuit has a 0V rail; it is the reference point for supply voltages, control voltages...
  19. KrisBlueNZ

    Electrical Engineering Major Student

    Hi Jonathan and welcome to the Electronics Point forums :-) I'm sure you'll find lots to interest you here.
  20. KrisBlueNZ

    Water damaged projector fixable?

    OK, it looks like that power supply has a power factor correction (PFC) stage, so it's really in three parts. Mains comes in through the bridge rectifier (marked GBU605) and is smoothed by a capacitor of a few µF, probably the rectangular blue component beneath the centre of the heatsink. Then...
Top