Shahriar

Dear indulis I have attached a file in my first message, (at the top of the Page). Its name is battery charger.PDF and has been downloaded 3 times. In which condition the output Current Will control th output voltage? :o Like a LM317 Over-Current Protection, It is always, the output voltage that controls the current to be Under i.e. 1A!!! ThanX Shahriar

Hi I attached that file to show that my device is going to work like the cicuit I have attached, the only difference is High current for my device. The circuit I have attached is a Current limited power supply. when The Battery wants to draw more that i.e. 1A the Output voltage drops to decrease current at 1A, when battery get charge the current decreases gradually down to Zero, thats when the battery has been charged to 13.8V, So it never get Over charged! My circuit is same just differs in Current (15A) and voltage (27V). Dear indulis I didn't undersatnd the Meaning of "" regulate it to no more than 15A "" Can you explain a little more!!! Dear Ante I hope I had answered your questions! ??? How much voltage is enough to charge a 24V Battery? ThanX Shahriar

Hi Someone has asked me to build a battery charger. The battry is a 24V / 150Ah from those kinds which is used in big vehicles. I think they Are called Lead acide battery!!! Am i Right? the battery is to be charged with a max Current of 15A! I decided to charge it with a circuit like the one I have attached, because of High current for my circuit, I decided to use TWO ATX (PC power supply) 12V rail. {They are 16A Nominal}, but the problem is how do I limit the current at 15A. I have an Idea, Tell me if it works: There is a pin in ATX Ps which is for Stand by, And PC pull it down to Start the ATX. I want to use a .05 Ohm resistor at the output and when Over-Current Happen, Pull this Pin Up? Can I have a current Control In this Way? Of course, I have to increase 12V rail of Two ATXs a little bit higher to creat 27V (13.5 + 13.5 Two ATXs in series) to Charge Batteries. ThanX Shahriar Battery_charger.pdf

Dear Perseus Antenna theory is very complicated and any Shape antenna has its own specification and uses, but as I have seen in some SIMPLE remote controls, the Antenna shape does not have very Specific impression on the range. I am going to build it for some one, If I did it, I will tell you about the antenna shape.... HTH - Shahriar

Dear Alun If it is not produced any more, Do you know any Substitute IC? ThanX Shahriar

Hi If you want to build a RF Remote control, i Think theis project will work fine. I have not build it yet but its design looks perfect. It belongs to 27MHz Toy Car. http://jap.hu/electronic/rf.html HTH - Shahriar

Hi There is an IC: "TDA7000". It is a complete radio IC. I couldn't find it in my area but I think you can. It is really easy to build a radio with using this IC. HTH - Shahriar

Dear SupeR-NovA About 330ohm Res. For a Flyback PS, and Vi(min)=190V, Your calculation is right. About the output caps, although there are some calculation for them, but As I have Seen in many designs, if you put bigger Value, it would be better. But about the inductor, as you Yourself Know, You should use the proper Value. I attach a file which belongs to a complete 250W Forward design, but because the complete file was too big, I extract just the page you need. (the complete document name is "250 Watt off-line forward Converter". There are lots of Such documents on the web. I think your design is perfect. Build it and test it. It will work fine. by the way, at any circumistances, you need a Resistor at the output to discharg the output cap. because when you decreas the voltage, the cap remain charged and if you connect a low voltage device, then ... HTH - Shahriar 250W-Forward.pdf

Dear SupeR-NovA I was planning to build the same circuit. you asked: "how much power should i draw from the supply when there is no load connected? " You should draw current as much as the Controller doesn't turn off. because Controller Is supplying from an auxilary winding. the problem that I think you have missed is that it is impossible to build an adjustable 1-30V adjustable SMPS while the controller is supplying from an Auxilary winding. because imagine the output is 2V the the auxilary should be i.e. 10V. now, if you inrease output from 2V to 30V then the auxilary will increase to 150V. (BLOW UP). you should use a seperate PS for controller then put a Resistor at output just for discharging output cap when you decrease the output voltage. you asked:" can i connect the 340v rail ground to the output ground or will this ruin the isolation?" There is a standard for SMPS called "VDE". it says that when the output is higher than 42V the output must be Isolated. For your project it is upto you. If you think it is difficult for you to decrease the voltage down to 1V with using Opto coupler and TL431 (which is impossible if using TL431) then you can forget Isolation! but if you are going to sell your project, Isolate one is better! ;) about current limiting, I think both of them are good but I think transformer one would not be very accurate. I am not sure about this. it is just a guess! I have seen in some schematic that they use the Output inductor as a transformer to determine Over current. There is a document on the web which it has good information for current limiting. it is 6.3Mb :o . Search for it. its name is "Current Sensing Solutions for Power Supply Designers" By the way, The output ripple of SMPS is much higher than a linear one at least 30mV. this is why I Decided to use a LDO at the output of the SMPS then Keep the SMPS output 0.2V Higher than the output. In this case the Power dissipation would be 1W at 5A. Some more benefits of this was: 1- the output ripple was very Very Good. 2- Accurate Current limiting was possible with resistor without increasing the output resistance of the PS. 3- I could decrease the output down to 0V. Because with using a TL431 and Optocoupler, it is impossible to decrease the output voltage lower than 3.7V. althought at lower voltages than 3.7V Power dissipation would Increase. but it is not a matter. HTH - Shahriar

Dear jeevan772006 Once I had made a distributor Amplifier with NE5532 IC. I had the same problem, after a few hours I found that I had not Place one of Jumpers which was related to -Vee Rail. So All of ICs didn't have a -Vee. As soon as I connected it everything went right!!! I was really surprised How it was working... ??? I don't know Wether your circuit has any -Vee or not, I just told this to remember Sometimes strange things happen... ;D HTH - Shahriar

Hi I want to build this Little transmitter. In descriptions,is written: " L1 = 9 turns, .15mm wire on 4.5mm diameter tunable ferrite coil former " 1- What is "tunable ferrite"? L2=15 turns, .5mm wire, 5mm diameter L3=3.5 turns, .5mm wire, 5mm diameter 2- Can I replace L2 and L3 with Equivalant RFCs? If yes, How to calculate it? ThanX Shahriar

Dear Ante I also have the same Oponion. It seems impossible. ThanX Shahriar

Dear Ante I think it is more clear now. If you didn't understand tell me to explain more. ThanX Shahriar

Hi A university expert has said that: Imagine a transformer connected to a Ac Voltage (between Phase and Nuetral i.e. 100V). it has an output of i.e. 12V ac. If you connect this trasnformer to the same AC Voltage (100V) which this ac voltage is comming from Two Phase which have 100V then the output will not be 12 V and is lower than That. {I mean, Imagine you have connected two Phase to a transducer and this transducer gives 100V rsm at its output then you connect this output to that trasnformer, Then The output will be lower} I myself have not tested this, it is just what that expert has said and asked to look for the reason? Is it possible? ThanX Shahriar

Dear smoknjoe44 Maybe using an InfraRed receiver and transmitter will do the job. when there is enogh Bin, the receiver does not receive anything and the LED will turn On. HTH - Shahriar

By the way, your transistors will get too much Hot because of 70W Power dissipation. you should use fan and some more Transistor in parralell and some resistors for current sharing. I hope you understand what I mean!!! HTH - Shahriar

Dear boombar I am not completelty sure but you can do it with those normal Regulator circuits. if you need a good regulation, maybe connecting some zeners in series and a suitable transistor with Vce >= 100V with high enough hfe. if you don't need 400V fix, then you can use two 30V zeners. just change the Resistor and zener place in the following Picture. HTH - Shahriar

ThanX all for your replies and your Pictures. At last I made this circuit working. I was sure about my circuit wirings and I was really disgusted. Do you know How I solved it. Look at the picture below: I don’t know much about Zero and Poles in Feedback circuits. But I think this cap will do something with Poles of the circuit. Before this I thought these poles are not very important….. At last I connected the output of circuit to Oscilloscope, Wow, without that cap that output was oscillating very neatly and as soon as I connected the Cap the output was a Clean +5V DC Voltage. I have attached the output signal without a cap. Dear Staigen ThanX vey much, I think you solved the problem. the time difference between your replies and when I read them, causes I work a whole day on circuit. when you type the replies I am sleeping and when I write questions, you are sleeping. at last If I had checked the ouptput with an Oscilloscoe then I would take result a 12hours earlier. 8) Dear Audioguru, are the values which you have written, from a circuit or you have witten them from simulating. anyway, I am going to test the circuit you have drawn. (I build the circuit on a BreadBoard!) :D By the way, when I just Inserted a 1nF cap between Pin3 and Pin1,(while there was no output cap) the output was still oscillating but the amplitude was smaller. ThanX All again Shahriar

Dear Staigen I put Different resistors there to ensure 2N4403 gets off. when I put a low resistor(2.2K even 330ohm) the output goes to 3.8V when I put a bigger resistor the output goes higher 4.8 But in both cases, the output changes when I change the Vi ThanX Shahriar

Hi I want to build a Low Drop out voltage regulator(LDO) I tried the schematic Below but the output Changes when I change the input voltage. I wrote the voltages I measured at Vi=8V. I put that 8.2K and 2.2K to create a voltage devider at the base of NPN tarnsistor because the lowest voltage i could get of TL431 was around 1.8V So I affrade maybe the NPN do not gets Off. I put the other 2.2K to creat Enough current for TL431. the output of this circuit should be 5V. The reference voltage of TL431 is 2.5V ThanX in advance Shahriar

You can Also creat a latch with D-Filp Flops. 7475. (Check it!) Anyway, there is a project in the Project section of this site. Its name is Park-Aid. Take a look. It will anserw to some of your questions. HTH - Shahriar

Dear MrHeckles One way to do this is to creat an average DC Voltage on the Vi+ of the Op-Amp. Beacuse there are lots of unwanted Spikes there. These method is used by New SMPS Controllers and Is called Average Current Control Topology. Anyway, without this, it is possible, but you should add a Low pass filter to The Vi+. Look at thescematic I have attached. HTH - Shahriar UC3843_Design.pdf

Dear wood_workur As your writing implies, you want to sell these devices to customers. On thing that you should remeber is that simple transmitters Frequency will change by Tempreture, and even after a month or a year. So if you want to get rid of customers calls, you should use a PLL based design. If you know programing, maybe you can use a Data transmitter to send address to enable or disable Devices, As I know, it is really difficult to use that Data Transmitter to send a digital Voice. (because of Low Baude rate of that transmitters) But if you do this, adressing will be very easy and you can increase the devices much more than 4. At last, I should say that RF designing need Exprience that I am sure you have Hope success Shahriar

Dear stevedabear As Ldanielrosa Said you'd better build one for yourself. About the file ANte Attached, I should say I couldn't download it because it is too big for me to download it. (I have a dial up connection) I have attached The thing you want. with all explanations. U can Download any other thing needed from the web site. but you should do that Old trick as we discused in this website to enables you to download from SILICON Website. Just Write the topic in Google and click on the Link. If you go directly to SILICON Website it does not allow you to download ;D HTH - Shahriar Silicon_Score_Board.zip

Hi I have a SMPS that its output varies from 4V up to 32V. As you know at the output of most SMPS there must be a Load to Dissipate some power. For my SMPS, it should be at least 2-3W Because this SMPS is to be used as a Laboratory Supply, I have to put a load at the output. I can not use a single resistor. i.e. Vi = 4V & R=8ohm ---> P=V^2 / R = 2W But if Vi = 32V then P= V^2 / R = 128W So I have to use a constant power consumption circuit. I designed one but it dissipate 8W at Vi=18V and dissipate 2-3W at Vi =32V and dissipate 3W when Vi=4V. I have not build it yet. These writing are from my calculates. This Non-Linearity is because P is proportional to Vi^2. Does anybody have a good Idea? The schematic is attached My numbers are not very Sharp ThanX Shahriar ConstantPower.pdf