Hero999

It depends on the power supplies. Some power supplies are designed to be paralleled but it normally means setting one as the master and the other as the slave. If you don't know then they probably can't be paralleled and will fight each other as audioguru said. You could try using a Schottky diode 'or' gate to parallel them at the expense of regulation and a voltage loss of between 300mV to 600mV depending on the diode and current drawn.

The transformer is not perfect and has an equivalent series resistance which drops the voltage when a current it drawn.

No. A remote contains an infra-red LED not a receiver. The wavelength used for infra-red remote controls is too short for monitoring the temperature of items near room temperature. You're better off buying an IR thermometer than making one.

Electrolytic capacitors are normally only made in E6 values, i.e. 10, 15, 22, 33 and 68 but some manufacturers only make E3 values i.e. 10, 22 and 47 which is why you're having problems finding 12,000

1200

How do you know it's cheaper than what I was going to suggest? I just gave you a worst case scenario of what it might cost. Care to redeem yourself by posting a link to it?

I think that the English spellings of some words is stupid, but if I suddenly started spelling every word phonetically, I'd get accused of being mentally challenged.

I don't buy any paper, I use old magazines for toner transfer, it doesn't matter whether it's printed on or not. Once you've mastered the process it's pretty reliable. Some people also have their own CNC machines. I imagine that if you have a laminator and a CNC machine then making your own PCBs becomes very easy and convenient even for double sided PCBs. I like to use SMT components because they save drilling. That's 25

I haven't seen any manufacturer that can make a custom board in quantities of one or two for less than I can. You mention iron-and-peel sheets; are you aware that you don't need and special paper? Many people swear by expensive proprietary papers or particular brand of photo paper but many don't realise that ordinary copier paper will work. My favourite paper is clay coated magazine paper because it's free and I've found it to be superior to copier paper.

I'm not going to go trough all your flamebait, I'll give you one last chance. I've only made a load of assumptions in the absence of any concrete information. I still don't know what your end goal is. Why haven't you told us? Is it a secret? You'll get more help if you had just provided this information from the very beginning. Slinging insults will not help your cause. I might have seemed to be arrogant but I can assure you it isn't the case, it's something you've assumed.I think you took my comments out of context, so what I'm probably more knowledgeable when it comes to electronics? I didn't mean to imply that I'm more knowledgeable than you full stop. You could be twice as intelligent as me for all I know. My point was that if you're asking someone for advice with something that you're having difficulty with then you should provide them with as much information as you can and not go on the defensive when they question your existing idea. Yes I am still willing to help you but only if you provide more information. For the final time: what is your end goal? I am asking this question for your own good because from what you've said, it doesn't sound like you're going the correct way of doing something. How do I know this? I don't really know for sure but I have this feeling because as far as I'm aware there is no real world application for a 12V 30A 0-15MHz AC PWM power supply.

In my opinion a Peltier cooler is not an option due to the excessive power required. Rather than a fan, is it possible to rely on the fact that the car is moving through the aire anyway? I imagine that using the car's chassis as a heatsink is probably the best option. You could probably dump quite a lot of heat into the chassis and hardly get any temperature rise at all. How are you gong to power the LED? I wouldn't recommend a resistor due to the excessive power dissipation. High power LEDs also often have quite a high voltage drop because they're actually composed of many smaller LEDs connected in series and parallel. For both reasons you really need a switched mode constant current power supply. As far as monitoring the temperature is concerned, I've noticed that the forward voltage drops with temperature which might in itself help guard against overheating if a constant current supply is used, if not you could cut the power if the voltage drop is too low. Usable lamp life is something you need to consider because LEDs get dimmer with age. I'd recommend underrating the LED slightly because not only does it make LEDs last longer, they're also more efficient at lower currents: running at 80% of the current rating does not normally reduce the brightness to 80% of the full rating, it's normally closer to 90%, see the datasheet to be sure.

Be patient, I don't sit at the computer 24/7! If it's one of those rediculas run your car from water schemes then you've probably been told that it won't work many times before on other forums. In case you've not been told before: electrolysis can't be used for perpetual motion because, burning hydrogen releases less energy than what is required to split up water into hydrogen and oxygen. If you just want to produce hydrogen gas then electrolysis is the easiest way for a hobbyist to do it. Some people talk a load of rubbish about how liquid water supposedly has a resonant frequency which can be easily excited to increase the efficiency of hydrogen extraction. The truth is that liquid water has no strong resonance, any resonance is strongly damped by the hydrogen bonds holding each molecule to its neighbour. Gaseous water does exhibit a strong resonance but the lowest mode is way up in the microwave band at 22GHz which is almost ten times the frequency used in a microwave oven. http://www.zyra.org.uk/microw.htm DC is best for electrolysis not AC. The ions in the liquid move very slowly so changing the polarity at a high frequency would just cause the process to reverse itself as quickly as it's happening with no electrolysis actually occurring. If you used a duty cycle of 50% the water would just heat up due to Ohmic heating. Altering the duty cycles results in electrolysis occurring equivalent to the average current flow. For example a duty cycle of 25% with a current of 30A will perform electrolysis at the same rate as a current of 15A, if the duty cycle is increased to 75% the electrolysis will still be equivalent to 15A, it's just the average current will be in the reverse direction so the oxygen and hydrogen bubbles will exchange electrodes. I think using a constant current source is your best bet. Pure water is also a very poor conductor because it doesn't have many mobile ions. Tap water isn't pure but it might not be ionic enough to work really well; to improve the efficiency of electrolysis you need to add a salt to increase the conductivity. You could use common salt (sodium chloride) but it would produce toxic chlorine gas and leave a nasty caustic solution behind.

There doesn't appear to be anything insulating the components from the heatsink which will need to be isolated from the metal chassis when it is cased unless the case is going to be non-conductive.

You still haven't said why. Is it a secret? There is no application I can think of. A DC motor will just vibrate and overheat. A resistive load such as a light bulb or heater will consume the same amount of power regardless of the duty cycle. It's possible you're trying to do something the hard way.

In my experience, toner doesn't stick to the board that well and can be easily scratched off so it needs a protective layer i.e. a conformal coating. Conformal coating is just a tough transparent lacquer which can be bought from RS Components and other similar shops. http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0569313

So now you want to do PWM? Why didn't you say so before? What do you want this is for? If all you're looking for is a motor controller you're probably better off buying one. http://cgi.ebay.com/DC-Motor-Speed-Control-Controller-12V-100A-Reversible_W0QQitemZ140357279312QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item20adf21e50

It's the high frequency requirement that's going to make it difficult for you. What on earth do you need 15MHz for? If it's just to drive a DC motor, it's far too high.

No offence intended but it's not very neatly assembled. If you put a bit more time into getting the PCB right you wouldn't have to solder some of those components so crookedly. If you made more of an effort to form the components properly then it would have made it easier to test and get working. If the soldering is a good as the component forming and placement then it won't be very reliable; making sure you solder neatly is important for reliability. A poorly assembled board can introduce many errors you wouldn't expect due to bad solder joints, bridges and shorting between badly formed component leads. I'm just saying this to help you so you make a more reliable project next time.

I've always used toner for the silk screen. To make it more scratch resistant I cover it with a layer of conformal coating.

Why bump a three month old thread? I often find that there are plenty of people who talk a load of rubbish and think they know what they're talking about. You're right of course about unregulated supplies but I can't see how, someone who has asked such a simple question, understanding the concept of voltage regulation.

Right now we're getting somewhere. I was going to say, I must have been under 8 years old when I built my first h-bridge. However I wouldn't have stood any chance of building a an h-bridge working up to 15MHz. What are you trying to do? How much current does the h-bridge have to supply? Does it really have to work all the way down to 0Hz? That is a pain because it eliminates using a transformer as a gate drive solution. I think that you might not have enough experience to accomplish this task.