Hero999

What level are you studying? This is pretty simple: use a comparator such as the LM393 and a temperature IC or thermistor. http://www.google.co.uk/search?q=comparator&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-GB:official&client=firefox-a http://home.cogeco.ca/~rpaisley4/Comparators.html http://en.wikipedia.org/wiki/Comparator

What do you want the inductor for? To connect to the 3A load? I don't see what adding an inductor to the low current regulator would achieve. The resistor just limits the surge current through the zener to a safe level, it just needs to be low enough to prevent the voltage loss from being too great. As it's only a 10mA load you could use a higher value resistor, 150R to 180R.

I've just Googled for Mastech 30V 6A power supply and I get lots of results. If the origional poster had given the model number, then I might've been able to find it and check that it says the maximum power rating in the specification.

Yes vintage cars can be especially bad at suppressing ignition noise. How much current are you drawing? What's the typical input voltage? I assume this is a 12V system and not a 6V system. Connect a 15R to 18R 0.5W resistor in series with the regulator. Connect an 18V 1W zener and 10μF capacitor in parallel with the regulator's input.

The low voltage of 1.8V is going to be the problem. What about using a precision thermistor?

They're not LEDs, take a closer look at the schematic. The pinout for the 555 is on the datasheet which can be found using Google. If you can't find the relay datasheet, and the pinout isn't clearly marked on the relay, it's quite easy to determine it yourself. The coil will have a resistance ranging from 100R to 1k and can be found by measuring the resistance between all the pins. The normally closed contacts will have a resistance near 0R. To find the normally open contact, energise the coil and search for a near 0R resistance. You need to use the normally open contacts. Note: make sure the capacitor is connected the right way round!.

Good, I'm glad you got there in the end.

You don't need image recognition or anything like that. A standard computer scanner is the cheapest way of doing it. It is possible to use an IR beam break or reflective sensor but it won't detect red pen.

What part of the formula do you not understand? t = 1.1RC t is the time delay in seconds. R is the value of the resistor in Ohms. C is the value of the capacitor in Farads, 1

Why not use a conventional scanner connected to PC and do the optical mark recognition in software?

The formula for calculating the time is on the schematic. As a general rule R should be between1k to 1M. How accurate does it need to be? Beware that typical electrolytic capacitors have a tolerance of 20% so even if you use values that will theoretically give exactly 4 seconds, the actual delay will vary between 3.2s and 4.8s.

Use a 555 timer.

What do you think? The circuit will obviously work as long as you're aware that the supplies on the right will not be isolated from each other and if you don't know what that means then I suggest you do some more research before building it.

How can it possibly be shorted when it's clearly open circuit? If you need to ask such questions then you obviously don't have enough experience to build it. I suggest you read more about basic circuit theory and Ohm's law and basic before building this project..

As Q5 and Q6 carry a considerable current, the PCB traces need to be thick enough to carry the current, otherwise it'll behave like a fuse. Of course the transistors need to be on a good heat sink. If the amplifier is driving a 4Ω load, the heatsink should be rated to at least 4

What do you think?

Connect the two power supplies in series and use the point where the two supplies are joined as the 0V point.

You can't do that with a single supply. You need to build two supplies and put them in series to make a +/- 30V supply.

I wouldn't advocate trying to help those with spam in their signatures.

What do you mean? Operating an op-amp with too higher voltage swing at too higher frequency will result in slew rate distortion which is nothing to do with the noise or distortion specifications.

For some reason my previous post was delete, maybe it was my mistake. I've retrieved it from the bin. The saturation voltage will always increase if the collector current is increased even if the base current is increased. A transistor is saturated when an increase in base current no longer causes an increase in collector current. MOSFETs are voltage controlled devices. If a MOSFET saturates, it means that it'll draw a constant current, regardless of the voltage across the source and drain. If a MOSFET is to be used in a switching application, saturation is a bad thing because the voltage across it will be high leading to a high power dissipation. To use a MOSFET as a switch it needs to be in the on state, i.e. when an increase in gate voltage does not cause an increase in current. There might be a more fancy name for this but I can't remember it. ;D

The 0V supply rail should be connected to the case which should also be connected to safety earth/ground. The inputs should be connected to whatever you're connecting the amplifier to with screened cabe.

Doryy, I don't know wht you're talking about.

Yes, that might help.

Try replacing Q5 and Q6 first, then Q3 and Q4.