Hero999

What do you mean Watts are J/s?

Agreed, it isn't very well drawn but it does seem to be correct. The correct and normal convention is for the positive power supply to be at the top and the negative to be at the bottom. Where possible real symbols should be used rather than the IC outline. The symbol for a comparator is show below. Why are you using the LM324? I'd recommend using a real comparator IC such as the LM393 or LM311.

You're not listening, you need a 30V transformer capable of supplying 4.2A

I think you need to be able to measure resistances lower than 100mΩ, perhaps 10mΩ? You need a constant current source, an amplifier and a volt meter. For example, if you use a 100mA constant current source, the voltage across the unknown resistance will be equal to 0.1V/Ω, adding a amplifier with a gain of 10 will make this 1V/Ω. You could use 0-2V a panel meter to measure the voltage across the unknown resistance which will give a reading from 0 to 2Ω. The voltage reading needs to be taken from as near to the resistance as possible to avoid the effects of voltage drop in the leads. If you make your own panel meter using a microcontroller you could add a zeroing feature. I would use AA cells to power the Ohm meter because a little 9V battery won't last for very long with a 100mA load; fully charged AA cells should last for a couple of hours.

Why would it be damaged? Use Ohm's law to calculate the current and power dissipation and choose a resistor with a higher power rating.

No single device can do all of that: you need a different sensor for each of those measurements.

Yes, that will do: Cat. MT-2114 25+25 Volts 3.2 amps 6.4 amps. Connect the two 25V windings in series to make 50V. Be careful, even the secondary side of the transformer is a high enough voltage to shock you, it shouldn't kill you but it will hurt.

The capacitors are in μF. Use a transformer with twin 24V windings. It's also possible to use a transformer with a single 24V winding but the rectifier needs to be configured as a voltage doubler and the filter capacitors need to be twice the size.

That depends on the size of the transformers, small mains transformers are very inefficient, typically 50% for a 1VA unit, larger transformers are much more efficient 98%. Superconducting transformers are 99.9% efficient.

It's a matter of opinion I suppose but I'm not very impressed. The colour scheme makes my eyes sore. I thought about going around copying loads of projects for Silicon Tronics but I decided against it, even if it would increase the amount of traffic. In the end I decided to slowly add more projects to it and not make too much of an effort because it's Dazza's site, not mine and I don't know how low he's interested in keeping it up for.

R1 and R2, and R3 and R4 form potential dividers which limit the gate voltage to the high side MOSFETs to a safe level, whether their values need to be changed for operation at 25V depends on the drain current at the lower gate voltage. The MOSFETs are normal enhancement MOSFETs with built-in diodes, if you're using this to power a large motor it's a good idea to add extra diodes because the internal diodes might not be fast enough. I don't know why you'd want to use IGBTs, at low voltages the on voltage loss is higher than MOSFETs, IGBTs are only any good for higher voltages >400V or so.

Sorry, I can't help you much with microcontrollers because I don't have much software knowledge. Here are some tutorials I'm currently reading. http://www.gooligum.com.au/tutorials.html http://www.winpicprog.co.uk/pic_tutorial.htm

Here's a schematic, no control circuitry is required assuming the lower MOSFETs are logic level. The diodes prevent both the high and low side MOSFETs from being on simultaniously.

50Hz is fairly low so it should be easy to level shift the h-side P-channel MOSFETs using BJTs and a potential divider or zener to prevent the gate voltage from being exceeded. At higher frequencies this sort of thing gets harder as the resistors slow the switching speed too much. I'll post a schematic if you don't get it.

It depends on the device and whether there's a lot of corrosion on the metal parts or not. Water isn't normally a problem unless it's very salty or the appliance is submerged whilst power is applied. In the electronics industry, circuit boards are frequently washed with water, it's normally deionised to help prevent corrosion. I don't have any deionised water and have washed circuit boards with tap water before drying with a hair dryer and I haven't had any problems. Wash the PCB with tap water to get rid of any dirt and dry it as quickly as possible. Inspect the PCB, repair any corroded connections and hope for the best.

I see what you mean, for speed you need a lot of power because it's exponential i.e. you get diminishing returns; upgrading a car engine from 100hp to 200hp won't double the maximum speed because drag increases with speed. Compensating for different wheel sizes can be done in hardware by using encoders with different numbers of counts per revolution. Suppose the back wheels are 150% larger than the front. If you use an optical encoder with 10 counts per revolution on the front wheel and 15 counts per revolution on the back, both will give the same number of counts per second at any given speed. When the back wheel does one revolution you'll get 15 counts from the back encoder, the front wheel will perform 1.5 revolutions so you'll also get 15 counts from the front encoder. If there's a difference in the number of counts, then there's some slippage. The phase difference between pulses from the front and back encoders should also be the same otherwise it's slipping. http://en.wikipedia.org/wiki/Rotary_encoder You'll also have to account for cornering, when you're going round a corner, the wheels on one side of the car will be travelling faster than the wheels on the other side of the car. Yes I think a PIC is probably your best solution.

50V@30A. I think you'll need to build the h-bridge from scratch from MOSFETs. How fast does it need to switch?

Have you tried LTSpice?

Why don't you just use the circuit from the datasheet? Always read the datasheet very carefully before implementing the circuit. As you've realised, you need a pre-amplifier so why not just look up non-inverting amplifier on Wikipedia and change the resistor values to get the required gain? To figure out the gain look at the datasheets for the transmitter IC and the electret mic.

I don't like that circuit myself, I prefer using a PNP and NPN transistor because the output voltage swing is greater. Look at the circuit where's the positive feedback? Try changing some of the component values. Why not use an IC comparator such as the LM311? http://www.silicontronics.com/index.php?action=ezportal;sa=page;p=17

I'm no expert but it seems like it's way overpowered. The engine isn't the only limiting factor on the car's performance, past a certain point, the transmission, wheels and chassis become limiting factors. If the engine is too powerful for the tyres then it won't be possible to operate it at full power because the wheels will always spin. In my view you should either use a smaller engine to save yourself the weight, use four wheel drive or better wheels/tyres so the engine can reach its full potential. Back to the original question: it's pretty easy to build a simple tachometer, a simple IR beam break or hall effect sensor could be used.

I don't see why you need to do this, the front and rear wheels should be rotating at the same speed. Surely there are better ways to eliminate wheel spin: traction control four wheel drive?

Why don't you ask your supplier? What's the power rating of the motor? Small motors are much less efficient than large motors so if this is an aquarium pump or a small desk fan motor then I wouldn't be surprised. The supplier might have given you the apparent efficiency, i.e VA/Pout rather than the true efficiency.

Don't forget to look at the datasheet for the transistor. http://www.datasheetcatalog.org/datasheet/macom/MRF171A.pdf It's probably designed for use in military radio equipment.

Are you sure they're incandescent lamps? They could be LEDs and have a built-in rectifier, does reversing the diode's polarity make any difference? If the lights don't work when the diode is connected in one direction then the lights already have a diode so you need to use a resistor or transformer.