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mixos

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  3. Convert 0-30V 3A PSU to 5A or more

    in Electronic Projects Design/Ideas

    Posted

    I build it and give me around 4A output max, but i didn't let it for long time. I have not made any measurements on ripple because i haven't an oscilloscope at home, but i will do the measurements as soon as possible and i will post the results here.

    What you suggest to use as a low voltage - high current load?

    Also can you drive us to the right direction to convert it to a 5A or more PSU?

    Q4 = 2N3055 it's rated at 15A max current as datasheet mentions. So it's ok to use it for higher currents. The changes must be done on other parts of the circuit. Am i right?

  4. Convert 0-30V 3A PSU to 5A or more

    in Electronic Projects Design/Ideas

    Posted

    Let's give a try to this:

    How can we convert the following adjustable power supply which is rated at 3A max to 5A or more. It has a current limiter circuit and 0-30V output.

    Curent Specifications:
    - Input Voltage: ................ 24 VAC
    - Input Current: ................ 3 A (max) ------> make it 5A or more
    - Output Voltage: ............. 0-30 V adjustable
    - Output Current: ............. 2 mA-3 A adjustable
    - Output Voltage Ripple: . 0.01 % maximum
    - Reduced dimensions, easy construction, simple operation.
    - Output voltage easily adjustable.
    - Output current limiting with visual indication.
    - Complete protection of the supplied device against over loads and malfunction.

    If we succed, it will be the best bench power supply available on the internet. Let's discuss the ways we can do that.

    You can find it here: http://www.electronics-lab.com/projects/power/003/index.html

    The schematic is the following:

  8. 0-30 Vdc Stabilized Power Supply

    in Projects Q/A

    Posted

    You will find a good Digital LED Voltmeter here :

    http://www.electronics-lab.com/projects/test/014/index.html

    It uses 7107 and can easily converted to a Digital Ammeter. Below i attach the basic connection diagramm with the connections as a voltmeter and as a ammeter.



    Also read this: http://www.electronics-lab.com/forum/attachments/Digital_Panel_Meter.pdf

    It's true that you need to connect a load to the output. Read this to understund how to current limiter works.

    Current Limiter Function

    Another very important feature of the circuit, is the possibility to preset the maximum output current which can be drawn from the p.s.u., effectively converting it from a constant voltage source to a constant current one. To make this possible the circuit detects the voltage drop across a resistor (R7) which is connected in series with the load. The IC responsible for this function of the circuit is U3. The inverting input of U3 is biased at 0 V via R21. At the same time the non inverting input of the same IC can be adjusted to any voltage by means of P2. Let us assume that for a given output of several volts, P2 is set so that the input of the IC is kept at 1 V. If the load is increased the output voltage will be kept constant by the voltage amplifier section of the circuit and the presence of R7 in series with the output will have a negligible effect because of its low value and because of its location outside the feedback loop of the voltage control circuit. While the load is kept constant and the output voltage is not changed the circuit is stable. If the load is increased so that the voltage drop across R7 is greater than 1 V, IC3 is forced into action and the circuit is shifted into the constant current mode. The output of U3 is coupled to the non inverting input of U2 by D9. U2 is responsible for the voltage control and as U3 is coupled to its input the latter can effectively override its function. What happens is that the voltage across R7 is monitored and is not allowed to increase above the preset value (1 V in our example) by reducing the output voltage of the circuit. This is in effect a means of maintaining the output current constant and is so accurate that it is possible to preset the current limit to as low as 2 mA. The capacitor C8 is there to increase the stability of the circuit. Q3 is used to drive the LED whenever the current limiter is activated in order to provide a visual indication of the limiters operation.

    As you understund you can measure the "preset voltage value" adjusted by P2 and convert that value to the corresponting current limit set point in a way.

    Hope that drives you to the right direction.

  9. Led display Digital Voltmeter question

    in Projects Q/A

    Posted

    I use this digital voltmeter with this

    3-30V power supply: http://www.electronics-lab.com/projects/power/032/index.html

    If you configure it at 200V range (R3 = 12K) then it will measure from 0-30V with one decimal point precision.

    for 4,1V will display: X04.1
    for 10,1V will display: X10.1

    where X indicates that the first display is OFF

    I think this configuration is ideal for your power supply.

    If you finally draw a PCB for a complete bench PSU solution i will be happy to host it under the power supply's page ;) .

  10. varible voltage, current limiting, power supply

    in Electronic Projects Design/Ideas

    Posted

    This power supply is exactly what i was thinking about. But it's difficult for me to desing it also :-\. Let's wait a more experienced user to drive us to the right direction!

    Meantime, i suggest you to read:

    0-30 Vdc Stabilized Power Supply With Current Control 0.002-3 A
    http://www.electronics-lab.com/projects/power/003/index.html

    which has current limiter circuit so you can take some ideas.

    Also i have to make another "feature" proposion:

    You can replace classic pontesiometers with DS1869 digital pontesiometers and have up down push buttons for adjusting the voltage.

  11. LED Flashlight

    in Electronic Projects Design/Ideas

    Posted

    That's a good idea converting a bulb flash light to a led one. It will become a power saving device with the same efficiency.

    If you visit:

    http://ledmuseum.home.att.net/

    you will find many interesting led flashlight projects.

    Also check:

    http://www.jens-seiler.de/bastelecke/jarlight-en.html
    http://www.web-ee.com/Schematics/LED%20Flashlight/LEDflashlight.htm
    http://www.e-f-w.com/community/modules.php?name=News&file=article&sid=32

  12. Transistor tester

    in Projects Q/A

    Posted

    You can check if 555 is ok by measuring the output pin 3. It must has a 12Hz signal. To do that you must have access to an oscilloscope or a digital multimeter that measures frequency. Alternativally you can replace 555 to be sure it's ok. Keep in mind that the most common problems are at the connections. Double or triple check them in different moments in a day so your mind is clear. Also make sure you really understand the connections reading the schematic and there are not confusions.

  13. Making PCBs with magazine's paper

    in Spice Simulation - PCB design

    Posted

    Dear billy

    I am glad to hear that this method works for you. I haven't tryed it yet myself. It would be nice if you scan your pcb and attach it to the forum, so we can see the quality of the result. I suggest you to use 300-350dpi resolution. If the pcb is big send as just a part of the pcb (use as high resolution as to keep the file size in acceptable size). Hope you can do that.. for us !! :D

  14. STi5518 Datasheet

    in Datasheet/Parts requests

    Posted

    I found some additional info about STi5518:

    Overview
    The STi5518 is a highly integrated single-chip decoder, designed for use in feature-rich mass-market set-top boxes. It integrates a high performance 32-bit CPU, a dedicated block for DVB/DirectTV transport demultiplexing and descrambling, modules for MPEG-2 video and audio decoding with 3D-surround and MP3 support, advanced display and graphics features, a digital video encoder, and all of the system peripherals required in a typical low-cost interactive receiver.

    To cover the needs of DVD-capable set-top boxes, STi5518 integration options include a CSS decryption block, a Dolby Digital audio decoder and Macrovision copy protection.

    An ATAPI interface support is built-in, supporting the glueless connection of standard Hard Disk Drives. In this way, the STi5518 is ideal for set-top boxes featuring trick modes such as live TV recording, pausing and time-shifting.

    The STi5518 is backward compatible with the popular STi5500 set-top box decoder, allowing easy migration from the previous generation.

    The high level of integration in a single PQFP-208 package makes the STi5518 ideally suited for low-cost, high volume set-top box applications



    Features

    Integrated 32-bit host CPU @ 81MHz
    2 Kbytes of instruction cache, 2 Kbytes of data cache, and 4Kbytes of SRAM configurable as data cache.

    Audio decoder
    5.1 channel Dolby

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