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EdwardM

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Everything posted by EdwardM

  1. Who knows? you could try http://www.electro-tech-online.com/viewtopic.php?t=8556 and others Ed
  2. Hi Paul SPST - Single Pole Single Throw - Otherwise known as an on-off switch. SPDT -Single Pole Double Throw - Single pole changeover switch, ie, with no power to relay, centre connects to one side. When power applied, centre connects to other side. DPST - Just two independent switches like SPST. DPDT - Just two independent switches like SPDT. Hope the illustration helps Ed
  3. Hi Jarmund personally I'd use a PIC processor, first use an op-amp with plenty of gain to amplify the sine wave so that it clips at the supply voltage - you now have a square wave at the input frequency. Feed this square wave into a PIC, ensuring that the input square wave is within the correct voltage range and write some software to measure the time between each transition of the input signal. You are then free to use the PIC output ports to give the digital representation in any form you require, you could have a software routine which will set the 4 bits based on a linear or other division of the input frequency range Ed
  4. Hi Dazza the light stays on on the floppy drive... usually indicates that the ribbon cable is rear about face Ed
  5. Hi Alun agree absolutely about the soldering iron. To Seth...buy the best temperature controlled iron you can afford, preferably one that can use different sized tips for soldering anything from battery terminals to 0402 resistors Ed
  6. Hi Alun hopefully there should be no need to use optos as it's all 12v supply Ed
  7. Hi Steve the only thing I would add to Shariars response is a slightly modified power supply Ed
  8. Hi Steve first problem, for me at least, is that I can't read the diagram as the quality is too low, can you post a higher quality image? Ed
  9. Hi Scott boredom is a good thing, it's amazing what you can learn I lean towards always finding the simplest way of making something work, apart from my earlier post, the next way forward would be to look at the next simplest way. With your specialized transmitters, if you or someone could measure the current drawn by the unit whilst in operation you could possibly use a simple resistor as a solution. For example, suppose a unit operated at 9v and 100mA and you wish to use 12v. In this case you need to drop 3v at the same current, this equates to (using Ohms Law) R=V/I, =3/0.1, =30 Ohms and with a power dissipation in the resistor of V*I = 3*0.1, =0.3 watts. So, a simple resistor would cure the problem in this case All the Best Ed
  10. Hi Scott my first thought is that you could take a connection from one of your 12v batteries and plug it in to the garage door button unit. I suspect that the difference in voltage would not be significant, ie, 12/9*100 or roughly 30% more, it really depends on the design of the unit and whether it is capable of withstanding the overvoltage. My first task would be to contact the manufacturer if you can and ask that question - on the answer will depend whether you need go to the trouble of making major modifications Best of Luck Ed
  11. Hi Nikolas try here, Fairchild is just one of many manufacturers of this kind of product Cheers Ed Added: here's a good site and the Google search I used
  12. Hi XYZ without going too deeply into the various points you raised, could you explain a bit more about your assertion... Ed
  13. Hi Alun looking at your original post, I can't help feeling that we also have the perennial problem that many of the people who post here don't have English as a first language and it is often difficult to determine, for me at least, what the question really is... I'm afraid I'm of the school of thought that says no, don't ignore it but provide more than enough information so that the poster will realize that they have a lot more research to do. This has the secondary benefit that even people of my advanced age get to learn something new/subtle almost every day. Ed
  14. sauna, luuverly ;D as you've seen the vce(sat) of the '3055 equates in resistance terms to 10 times greater than that of the BUZ11, however there is a slight trade-off in that the gate-source capacitance of of the BUZ has to be charged up before anything useful can be done and this means power wasted, I still lean toward FETs in dc-dc converters I really must build myself a sauna Ed
  15. Hi Bjorn mosfets and transistors are quite different as you've seen, but in a switching configuration you could equate the two parameters, ie, Vcesat = 1.1v@4A is equal to a resistance of 0.28ohms and Rds(on) = 0.03ohms Didn't Liverpool do well Nothing foolish about the thoughts Ed
  16. Hi Dan sounds like a fun project. To be honest, if I were designing this, I'd use a combination of a stepper motor/gearbox and microcontroller. The stepper would give you precise control over speed (presumably moving at 1/12 speed?) and the microcontroller would allow the use of some sophistication in switches and lift positioning. What's the timescale? Best of Luck Ed
  17. Hi John circuit as shown below. To reiterate, max current into load is 80mA which aint much so you may need to drive a small relay or transistor first to make your solenoid work. (If you need help with that, come back) Best of Luck Ed added second drawing just in case
  18. Hi one of the ways of driving a LED matrix is to use dedicated IC's from various manufacturers, for example: http://www.maxim-ic.com/appnotes.cfm/appnote_number/1033 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1339 and this one http://noisybox.net/electronics/LED_sign/ Best of Luck Ed
  19. Hi John, you haven't said which SMC switch it is but looking at some of them it appears that the output current available is less than 80mA which means that you could drive a small relay (solenoid) and use its high current contacts to drive something bigger, it really depends on which switch you have and the power needed by your solenoid. SMC seem to do a hugh range and some are PNP and some NPN open collector output. Really need to know which one Ed
  20. Hi can you post a data sheet for the DP switch?, it may be that there is insufficient current avaiable or something else. If you can provide a sketch of your circuit, that would be helpful too Best of Luck Ed
  21. Hi GreekPIC I've been promising myself for years that I'd build a CNC machine ;) real soon now. Apologies if you've already done so but could you post a picture of the mechanical aspects of the machine? Thanks Ed
  22. Hi GreekPIC this link will give the the complete answer as to why the DVM reads anywhere between 470k and 2.7M Ohms http://www.pge.uk.com/PGE/pdf/KNB153x_R.pdf Ed
  23. I didn't wait long enough for my latest post to upload... :P and it got lost ??? What I said was that the output from the transformer is AC. And the action of the diode is to provide both DC and secondarily, a nice word for this time of night, to prevent the capacitor discharging back through the transformer secondary. Ed
  24. Hi Shahriar the first thing I can see is that R1 isn't really doing anything apart from being a current dump for the bridge rectifier. If you want to limit the inrush current to the reservoir capacitor then a resistor should be placed in series with the capacitor. It may be that most of the available current is being lost in R1, remove R1, and check the output voltage again and post it Best of Luck Ed
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