Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Search results for query: *

  • Users: lcsjk
  • Order by date
  1. lcsjk

    Circuit to simulate a computer cooling fan?

    Reducing the voltage with a resistor and or diodes will help reduce the noise. Search the internet for cooling fans. Look at Nidec. Search the major distributers such as digikey, allied, newark and mouser. There's lots of others. If the fan blades are too close to the grill or slots, they...
  2. lcsjk

    Voltage drifting

    I think you need to make sure the strain gauge instrumentation works correctly when hooked up under lab conditions. Also, make sure your connections are good. Is it possible that you might have an "open circuit"?
  3. lcsjk

    tri-state bus

    A tri state output has one transistor to pull the output to ground and another transistor to pull the output to VCC. Only one of these transistors will be on at any one time so that the output is either high or low. Although only one can be on at any time, they can both be off at the same...
  4. lcsjk

    Calculating battery life

    Kennyden, you need one little bit more information to get your final answer. The battery capacity rating is called the C-Rate and is the current that the battery can sustain for 10 hours before dropping to the "fully delivered capacity" voltage. This means that your 3135mA-H battery can...
  5. lcsjk

    Fuse change

    No. 1. Your analysis is probably correct. No. 2. You have a pico fuse, soldered in. It is not easy to replace so it needs to be heavily over-rated. Nuisance failures here translate to lost customers. Over rating is used to protect by taking the circuit off-line, and is not intended to...
  6. lcsjk

    Ground rings on PCB's

    I agree with geezer. Even though there could be some reasons or special conditions, I have never seen it used during the last 30 years for anything other than helping to make a good connection to earth ground. It will not help any EMI problem although it probably will not hurt.
  7. lcsjk

    HELP : AC to DC circuit

    I doubt that you can build this one as cheaply as you can buy it. Look through the pages of power supply manufacturers. Simple low-cost switchers will do your job and many have remote sense imputs that will allow you to adjust the output voltage from 12 to 10.
  8. lcsjk

    5V/24V DC-DC converter?

    Look at Vicor's modules and search for the look-alikes. THey don't need much more than capacitor's to complete a DC/DC.
  9. lcsjk

    How to increase output current of OP AMP

    Integrated voltge regulators can provide the current and limiting along with overheat protection. For precision, you can use an op-amp to power or change the reference voltage pin of the regulator, and provide voltage feedback to it. YOu might find that you do not need the extra op-amp. Check...
  10. lcsjk

    Z80 Microprocessor w/ Floppy drive

    The Z80 is a nice simple chip, but you might want to investigate one of the simple micro coltrollers in the motorola 68HC05 family. It's programming will be similar to the Z80, and you might find circuits for the Floppy controller there also.
  11. lcsjk

    choosing an audio amplifier

    You need to study a good bit in order to pick up the design differences in these, however: A class A is a linear device with characteristics similar to those of an op-amp with higher power. In this case the output is on all the time, either driving or sinking current from the speaker load...
  12. lcsjk

    driving transformer primary

    Whoaa there folks! Let's don't get too carried away with this one! The impedance of a 100 uH inductor at 100 KHz is 2*pi*freq * Inductance, giving an impedance of 251 ohms for this transformer for a sine wave. That tells me that 5 volts can only drive 20 milliamps into the primary with an open...
  13. lcsjk

    where is the best place to buy parts?

    Digikey - Excellent inventory, but not ztx321. Excellent for getting data sheets. Mouser - Good inventory Allied Electronics - Major Distributer, been around since the '50s Newark Electronis - similar to Allied. Jameco - Fair inventory, but has some unique items Don't forget www.google.com...
  14. lcsjk

    Driving a FET via a micro

    REad the data sheets! St7 cannot drive 25mA at a level to turn on/off the mosfet at high speed, and indeed without a limiting resistor you may violate absolute specs. Make sure you have a limiting resistor on the output pin to limit the current to its max level though (not less than 200 ohms...
  15. lcsjk

    Current Amplification.

    Not sure if you are using the 339 for an amp or a switching comparator. However, the 339 is not internally compensated for linear operation so you need to put a capacitor in the feedback loop (output to (-) input. Remember that you are not current regulating but are regulating the voltage...
  16. lcsjk

    What colour are plus and minus?

    You are referring to international product safety standards. Search the internet for "product safety" and words like ISO, UL, CSA, CE, TUV, VDE, DEMCO. This gets most of the main worldwide usage for standards.
  17. lcsjk

    0-10V to 4-20mA

    The op-amp gets hot with no load because its output is having to sink the total current that would normally go to the load. A higher gain transistor, such as a darlington, and a resistor from op amp to transistor base will solve the problem.
  18. lcsjk

    slow switching relay

    Your description is not very clear, but here is what I think you are doing. When your thermostat reaches its threshold it makes a contact closure or energises its internal relay. AT that time you need to provide a 2-second pulse to the cooling unit to start it. At the end of the two seconds...
  19. lcsjk

    Circuit for DC to DC Convertor.

    A 120 VAC switching power supply steps up the voltage to either 170 volts or 340 volts based on its topology. A 220 vac input PS rectifies the input to a voltage between 280 volts and 310 volts. So if you want to use a commercial power supply, you will need a unit with only one input capacitor...
  20. lcsjk

    Help with building a current supply

    Look at the first stage of that circuit. It is an op-amp driving a PNP transistor, and is a current source. Using that circuit topology, change the PNP to a P-channel mosfet, and add a gate source resistor of about 2k. Change the 1 ohm resistor to a 0.05 or .01 ohm resistor. It will be a...

Part and Inventory Search

Back
Top