Shahriar

Dear Alun I am designing a high current Power Supply. If I put a resistor in series with PS and sense the dropped voltage across it, then I have increased the output resistor of my power supply. ??? the PS is a SMPS. I don't know whether I can calculate the current from some where else or not? How does Ameter in digital Multimeters work. they can sense current down to 5uA or maybe less. do they use a Shunt resitor or do another trick? ThanX in advance Shahriar

Hi I want to build a Digital Ampermetre upto 5A. Does anybody know an IC for this purpose. ThanX in advance Shahriar

ThanX all for your repeplies. Today I saw a SMPS circuit that the OptoIsolator Works some how differently and work in ON/OFF Mode as Alun said but the Controller IC also is Different. When I get sure, I will Send the PDF to SMPS section. Dear harrychoo As I have seen in most circuits, Specialy TV Power section, for Over current protection (OVP), they use a a small resistor between MosFET Source Pin and Ground, then check the voltage across it. I have not seen a SMPS to control the over current by OptoIsolator. Dear Audioguru Can you please explain some more about Frequency Compensation. Where did the designer bring these Value? (10K Resistor and .01uF Cap) ThanX Shahriar

Dear Mr.SONY I have Seen in TV documentries that the scientist connect a transmitter to a dead Fish and put in on the lake. then an Eagle comes and take the Fish. then the scientist Find His/Her Home via a special Receiver. How that Receiver Work? I Think this is worth to work On. At a Glance it seems to be easy, A topology is the first problem and RF designing is the other problem! But the main problem is that, you need an Eagle to test your project ;D HTH _ SHAHRIAR

ThanX all for your replies dear Alun I don't think that the opto Isolator turns completely on or turns Completely off, but the emission of the Transmitter veries, then the Collctor-Emitter Resistance veries so the voltage at Pin(-) Of OpAmp Veries and the diffrential voltage will be amplified with a Limited Gain. the Amplified voltage will cange the duty Cycle. (*) If the Emitter was to switch On and Off, then there was no need of a Feed back for the OpAmp. But two questions : 1- what is the role of the 10K Resistor and .01uF Cap. 2- When the emitter gets dim, how does the circuit Forces it to bright more? ThanX in advance Shahriar

Hi If you take a look at TV or Monitor power supplies, you see a circuit Like the one I have marked red in the picture. In the SMPS guide which I downloaded from SMPS Disscussion of this forum, there was the explanation I have write at the bottom of the picture. Can you explain how that circuit compensate the Tempreture Drift. Usually there is a transistor somewhere there that the MCU sends the PS to standby Mode through it in TVs. ThanX in advance Shahriar

Dear K....21 I have a program which is for Audio editing and in a section it has an Equation Builder. In this section the software will generate a signal proportion to the Equation you write, then Plays it. (i.e. 3Sin(2*PI*f*t) ) You can receive the signal in Sound Card ;D its name is Goldwave. If you look it up in web i think you can find it. anyway if you think this is what you are looking for I can send it. But I think it is not difficult for you to write such Program HTH - Shahriar

Dear Audioguru Sorry, I didn't mean that you can draw 25A from One power transistor. (I had Mis-spelled ;D) If you want to draw 25A you have to use 4 or more 2N3055 (depending on Input voltage and output voltage, {VCE}). anyway if the your power supply works fine as much as you expect, then No problem, that's yours ;) Shahriar

The main problem in SMPS Designing is the transformer calculations. The best thing you can do, is copying from a TV schematic and buy the transformer. because finding the TV transformers is not very difficult. and the schematic is on the WEB ;D HTH - Shahriar

Dear moutoulos It would work but I think something is happening. Those regulators are not Exactly the same. for example the first output is 5.25V and the other is 5.20V. then we would have a current from the first IC into another on. this also causes that all reulators do not give the same power. If you connect the output of each one through a diode then maybe some of the problems get solved. (MAYBE) but using a regulator and a Power transistor will be much more better. HTH - Shahriar

Dear KAD I think you can not do anything with beams! because any interrupt will cause the counter to count One. You'd better to deactivate the counter circuit. for example if you have a TTL IC in counter citcuit, maybe you can deactivate it via CE(Chip Enable) Pin. If you have not build the circuit yet, maybe It would be much more easier if you do the project using a MCU. HTH - Shahriar

Thanks All, By the way; I have not tested this. If we look at a LCD Display through a camera, Does it Have Black Lines? Maybe this question is because I do not know enough About LCD; ThanX Shahriar

Hi When I Look at my monitor through my Mobile Camera I see black lines going up. As I go far from monitor then the black lines will go to disappear. the same thing happens when I record films from TV with my Camcorder. which is the reason? 1- Because the vertical scan frequency of Camera differs from Vertical frequency of Monitor Or TV? 2- If we imagine that both Vertical Freq. of TV and camera the same (i.e. 50Hz), then because they are not Syncronous, we see these black lines? ThanX in advance Shahriar

Dear konsempu This is the schematic I used. I omitted the parts which you didn't need, {Beacuse I was building a Fishing Buzzer} The schematic you see is just the Buzzer. the Left part is an Sine-Wave Oscillator the right part is the driver. the transformer is a simple Audio transformer. it is there to increase the voltage. you can pull down the base of the transistor with a pot to control the volume. Becarefull the transistor not to get too much Hot. you can use power transistors. hth - Shahriar

Sorry, I coudn't find the datasheet in my PC, You can download them from Internet

Dear santi_king Building data Transmitter (Tx) and Receivers (Rx) is very difficult. so you can buy some Pre-Built Modules and use them in your project. the most famous is TLP434 (transmitter) and RLP434 (receiver). In my area there are some other Kinds. I have attached the datasheet of both. the Only thing you should do is to define some Codes. For example (2CH for Right Command, 2DH for Reducing Speed and ...) then you send these commands to the Car and the Micro will do the job. If Range is not big problem you can USE IR (Infra - red) transmitters. HTH - Shahriar

Dear Audioguru This small camera has two RCA outputs. One is White (Audio) and the other one is yellow(Video). if you connect these two jacks to the TV Input RCA Jacks then you can watch what the camera is capturing. My understanding of what I have read is: the Signal which the Video Jack is carrying is called Composite Video Signal. the Composite video signal consists of 1- Luminance(Y) 2- R-Y 3- B-Y 4- Vertical Sync 5- Horizontal Sync 6- Some other pulses for Color detecting The composite signal is a Base-Band signal and it is not Modulated so the highest frequency is around 7MHz I really Do not know the exact meaning of FBAS but when you look at TV schematics, I usually see the signal coming from RCA Input Jacks is called FBAS and sometimes CVBS. (all of these is around Video Processor IC in TVs) I have attached a Datasheet which is related to an IC used in some kind of Old TV for detecting RGB. The Typical PAL decoding Application in page 7 shows how to detect RGB from Composite video signal. If I am Mistaken please tell me! As I said, I am going to use this Camera for Controlling a robot. This is why I want to detect RGB Signals. ThanX Shahriar TDA3562_-_Payam20_Video_Processor.pdf

Hi I have a small Camera that its Output is a RCA Audio/Video Jack. I Plan to design a circuit which can detect: 1- RGB Signals 2- Horizantal Sync Pulses 3- Vertical Sync Pulses. I know how to detect Horizantal and vertical synce pulses. but detecting RGB signals is a little bit confusing. there are too many ICs which most of them are used in TV and i am a little bit familiar with them but I can not decide which one is the best. the circuit should be as small as possible because it is going to be placed on a small robot. ThanX in advance Shahriar

Dear santi_king You can Buy a pair of those RX and TX modules Like TLP434 and RLP434 then send data to your MCU. then your MCU will be enable of controlling the PWM and your stepper motor. HTH - Shahriar

Hi I am confused between these two signals: FBAS or CVBS. when I take a look in TV schematics I saw them very similar to each other but in a schematic it is written FBAS and in the other one is written CVBS. Can you tell me the difference? 2- What is the frequecy of these two signals. I think CVBS is the signal coming out of the Video JACK(RCA) in the back of VCRs or TV outputs. Is the frequency of this signal Base Band or IF (34.8MHz I think) ThanX in advance Shahriar

There is a good one in the project section with this topic "PWM Motor/Light Controller " here is the schematic: I have a MCU base PWM Controller with LCD and keyboard. IF you know programming I can send it to you.

Dear AudioGuru If You put your TV set somewhere in Sunlight you will see nothing happens to its IR remote control. I have tested many IR receivers and have seen that some of them acts like a LDR when there is no IR Emitter. The best Receivers are TV IR receivers. they are much more expensive than normal IR receivers. some kind of them have Three Leads. P.S. If you take a look at note section in Park-Aid Project, then You see that Author have the same Oponion. "The infra-red Photo Diode D2, should be of the type incorporating an optical sunlight filter: these components appear in black plastic cases. Some of them resemble TO92 transistors: in this case, please note that the sensitive surface is the curved, not the flat one." HTH - Shahriar

Hi There is a robotic contest in my university and I want to build a robot with high reliability. But Robot Mechanics has been always Dusgusting to me. The robot should have high Speed, high Power and As Small as possible There is no limit for Power supply because we are NOT going to power it from a bettery. If Anybody Know a good Mechanic, then I would Appreciate it. ThanX in advance Shahriar

Dear ahtesham_rulz In my area this problem is solved in Traffic Lights. My friends use some sensors which are similar to wires. they put them across the road and hide them. they are sensitive to vehicles. If you look for these sensores then it makes everything very easy. using Laser or light is not good because of Sun light as others said. anyway, if you use IR then then it is possible that when people cut the IR, You mistake it with a Vehicle. but IR is much more better than Laser and light. P.S. for your IR receiver use those Kinds that are not sensitive to Sun light. i.e. TV IR receiver. some kind of IR receivers are sensitive to Sun Light. HTH - Shahriar

Hi The Most importat parameter between The DC power and Output power in a transmitter is called Efficiency. the best transmitters have efficiencies near 60%. the Efficiency = Output Power / Input power The most power disspation occures in RF Amplfier Section: Class E RF amplifiers have the best Efficiency. Anyway I recommand you to use a Long range remote control because they have a SAW resonator and works an 433Mhz or higher and have very good stability. If you build one yourself without a resonator then It is possible that sometimes your Remote control doesn't act because of the oscillator Shift Frequency and the person in Ambulance say goodbye to everybody :-(( HTH - Shahriar