Hero999

The voltage marked on the capacitor is its maximum voltage rating. Using a capacitor with a higher working voltage than is necessary is good practise because the component will be under less stress.

Why would you waste money on 200W? Read the specification.

Yes, as long as the transformer is rated to 70VA or more.

The propper way to do this is to use a centre tapped transformer and draw the power from the centre tap when the output voltage is set below 6V.

It's a dangerous design. The DC side should be isolated from the AC. The easiest solution in this case is probably to use an optically or pulse transformer isolated TRIAC to perform phase control on the AC side of the rectifier.

I read your post. I just don't see why i should help you when you can't even be bothered to post the schematic and datasheet.

The old IRL540 will probably do but the VDS may be too high for what you're doing. Any of the following transistors will be able to switch 3A with 3V. http://www.onsemi.com/pub_link/Collateral/2SK4043LS-D.PDF http://www.irf.com/product-info/datasheets/data/irl1104pbf.pdf http://www.irf.com/product-info/datasheets/data/irl3103pbf.pdf http://www.irf.com/product-info/datasheets/data/irl2203npbf.pdf

How are we supposed to know? You've posted no schematic and no information about the gas sensor or any of the other components you plan to use.

There are plenty of MOSFETs which will switch 3A with a gate voltage of 3.7V. The old IRL540 is has an RON of 0.11Ohms at VGS = 4V and ID = 14A. With a source voltage of 3.7V it'll be a bit worse but you only want to switch 3A so it should be fine. What's the lowest battery voltage? It sounds like you're using L-ion? The trouble is it may not be good enough when the battery voltage is low. Going from the datasheet it appears it should be fine down to 3.5V. http://www.vishay.com/docs/91300/91300.pdf

Then you need to learn more. Why not post a link to the schematic you've found so we can explain it to you.

Audioguru designed a better transmitter while ago. Here's a link to the project. http://www.silicontronics.com/index.php?action=ezportal;sa=page;p=15

It's an RFI filter.

Here's a link to a very simple ultrasonic proximity detector. It works by sensing the amplitude of the reflected signal which isn't very good because it's dependany on how well the object refelects the sound as well as the distance. The output is either on or off which isn't very good either. http://pecworld.zxq.net/Assets/SOURCE/PDF_fun_circuit/All_pdf_files_manual/167_Dec06_01.pdf A more complicated proximity sensor would measure the delay of the reflected signal and produce a tone varying in volume or frequency. It would also be good if the intensity of the reflection is indicated so the user knows whether the object is soft or hard.

Yes, a cable gland will work. Most electrical suppliers sell them. YOu could use a small plastic enclosure for the PCB and put the fibre optics in the gland opposite the PCB.

How are you powering the transmitter?

I don't think it'll make a difference whether you use wire or resistors. A lower flow rate would certainly allow a higher temperature rise. It would be also more efficient if the air intake is non the other side of the hand so the air is recycled.

I think it's worse than that. 1ft = 30.48cm 1ft3 = 30.483 = 28316.85cm3 which works out at around 1.2kW. This makes sense when you think about it. Look at the power rating of a typical hair dryer and you'll find it's in the region of 1 to 2kW. A halogen lamp will be more efficient than a fan heater because it only has to heat objects immediately in-front of it, rather than the air which is then used to heat the object. With a radiant heater the air can be at a much lower temperature than the objects being heated, for example on a hot day the air may be 35oC but the road temperature could be 65oC.

It depends on how the charger works. If the actual charging circuitry is built-in to the Zune then all you is a power supply with a voltage of around 5.5V and a rated output current of 1.4A or more. The charger will just use as much current as it requires. The internal control circuitry should requlate the actual current supplied to the battery. If the charging circuitary is external to the Zune you need to buy the correct charger and using any other charger may damage the batteries.

The amount of power required is determined by the flow rate and desired temperature rise. According to Wikipedia, air has a volumetric heat capacity of 0.00121J/cm3 under standard conditions. This means, if the flow rate is 1cm3/s the amount of power required to raise the temperature by 1oC is 0.00121W or 1.21mW. http://en.wikipedia.org/wiki/Heat_capacity#Table_of_specific_heat_capacities You need to know the flow rate of the air from the fan, the minimum room temperature and design a heater which provides a little more power than the minimum power required to heat the air. If you want to regulate the temperature, you need a temperature sensor and some negative feedback in the PWM controller. To avoid overheating the fan it should ideally be before the heating element, i,e. it should suck cool air in and blow it over the element. There shouldn't be a problem as a typical computer fan should be able to operate up to 60oC anyway. For safety reasons there should be a thermal fuse and bimetal strip to cut power to the heating element in case the temperature controller fails and the air heats to a dangerous temperature, causing burns and fire. Have you considered modifying a hair-dryer? It may be the cheapest option but there are obviously more safety hazards: mains voltage and higher power.

You're generally better off not connecting the 0V rail to chassis because you don't know what the 0V rail of the device you're powering is connected to.

Your description is too vague. By the sounds of it you want a toggle on/off i.e. a divide by two counter rather than an XOR but it could be anything.

The circuit in question only lights the LED briefly when enough energy has been gatherd. It doesn't continuously light the LED brightly. You can't create energy from nothing, for example, there isn't a circuit which would allow a single AA cell to provide enough power to boil a kettle and the same principle applies here.

I couldn't find a datasheet but a Chinese site is selling them and provides some technical data. http://www.aliexpress.com/product-gs/447102475-IC-chip-new-SE336-wholesalers.html Perhaps you could ask them for a datacheet.

Are you just trying to power the LEDs from the transducers? If so you need to add more transducers or increase the force or speed of the mechanical action. Adding a transformer will increase the current but the voltage will be lower so may not be high to light the LEDs. You need more power. The only other way would be to use an amplifier which requires another power source be it a battery, solar power or the mains. You can't create power from nothing.

Plsea post a schematic of what you already have.