Hero999

There's no need for a solid state relay. The signal is AC and the voltage swing is less than the power supply voltage so you can bias the signal at half the power supply voltage and AC couple the input and output via suitably sized capacitors.

I have a problem with my car. Is it the battery that's bad or the ignition coil?

The gate switch should never go above of below the negative rail. It should be connected to 0V to turn off and +V to turn on and should never be left floating. An analogue switch is not a solid state relay. The signal being switched should always have a voltage within the supply voltage range and should be referenced to the IC's 0V rail. The on resistance of the 74HC4066 also varies depending on the voltage of the signal being switched which can cause considerable distortion is the load impedance is low enough. How fast do you need it to switch?

No, the voltage on the capacitor will be about 32.5V with a 24V transformer.

That makes sense. The original poster really needs to learn how to use alldatasheet.com, datasheetarchive.com, Google etc.

What about tuning the RF oscillator on and off?

He's probably right though, normally lethal voltages at lethal currents aren't allowed at these events. I bet you weren't allowed to generate dangerous amounts of hydrogen gas. If wasn't a Brown's gas improve the efficiency of your car project was it? ::) Anyway, back to your original question: can I get 250VDC from a variac? Yes, it's possible and is pretty easy, providing it doesn't need to be regulated. Are you sure the output from the variac is 0 to 300V? I'm only asking because it seems an odd voltage for a variac., normally you get the input voltage plus 10% to 20%, there again with no load connected, it'll probably be a bit higher. Do you measure the output from the variac on or off load? Does the DC voltage need to be regulated? How important is ripple? You need an isolation transformer, to isolate the output from earth ground, for safety reasons. Here's the simplest solution: Add a transformer to convert the voltage from the variac to 0 to 180VAC with a current capacity of >2A. Connect a bridge rectifier and a filter capacitor to the secondary, to convert the AC voltage to DC. The output won't be regulated and will have some ripple.

It's not found on Google. It looks like a relay, I doubt you'll be able to get a datasheet for it but you can probably easily figure out the pin out using a multimeter. If it's not a relay, then I have a feeling, it could be an IF filter, probably 455kHz. What does the board do? How about posting a picture of the whole board?

Anti-virus doesn't give as much protection as most people think. Don't forget that before a an anti-virus program can detect and remove a virus, the programmers need a sample of it, which they only normally get hold of after the virus has infected 1000s of computers. Memory resident virus scanners also have the disadvantage of slowing your computer down, especially when they're downloading updates.

What are EHPs? A simple transimpedance amplifier can be made using an op-amp and a resistor.

It depends on the holding voltage of the solenoid and how long it needs to be on for. Use the following formula to calculate the capacitor size: C = t

The problem has now been solved. Google periodically scans all sites it crawls for viruses and adds any bad sites to a blacklist. Firefox has a security feature which automatically blocks blacklisted sites, therefore reducing the risk of getting a virus. The text now appears on the screen much faster but it still isn't quite as fast as other sites. I haven't tested this with Internet Explorer so it could be a compatability problem with Firefox or the extensions I use.

It seems like Electronics Lab has been reported as an attack site. Every time I visit this place I get the following warning from Firefox, see attached. I wonder if this is because of the amount of spam that the bots post here? One thing I have noticed is that this site does seem to be slower than others; there's a huge delay between me pressing a key and the letter appearing on the screen and I have to wait a long time for the display to catch up with my typing, it's ike using a really old computer way back in the 80s.

I've assembled the PCB now. I haven't tested it yet though.

Please don't spam the forum by asking the same question three times. Well, to be picky, there's no such thing as ultrasound radar; detecting object with sound is sonar, radar uses microwaves. Read the second reply to this thread: audioguru posted a link to a sonar project on this site. I have not built it but I have not heard of any problems with it.

Yes, I've seen many proprietary silk screen products but I've never used them. They look nice but they're also more expensive than simple toner transfer. I think black is fine for a silk screen, it does the job and I've seen professional PCBs with a black silk screen. Here's a link to the lacquer I use: http://uk.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=569-290&x=0&y=0 My only concern is that it might not be resistant to isopropanol or acetone which I use to remove the solder flux from the board. I might have to switch to a solder with water soluble flux. Here's a PDF of the schematic and PCB layout. I noticed an error in the PCB after etching the board, I forgot to connect the op-amp's 0V pin, the error has been corrected on the attached file. Here's a link to where I borrowed the design for the low pass filter from http://sound.westhost.com/project11.htm Noise_generator.pdf

Ideally you need a 5V regulator with a drop-out voltage <1V@50mA will do. As I said before you could use the LM7805 which has a typical drop-out of 1.5V@50mA but the battery will only last for about 8 hours. You can buy the LM2931AZ-5 from Futurlec which is based in Thailand and ship globally. http://www.futurlec.com/Linear/LM2931AZ-5pr.shtml

Attached are some pictures of the PCB for a noise generator I'm currently building. I used the toner transfer process with magazine paper. For the silk screen I covered the toner with a thin conformal coating to stop it from being scratched off. It isn't perfect but it's good enough for me - the traces all etched perfectly which is the most important thing. Although I've experimented with printing a silk screen before, this is the first time I've done it for real. As you can see it isn't perfect. The toner all stuck perfectly, but some bits came off when I cleaned it so I filled in the gaps with a permanent marker which ran when I sprayed on the conformal coating. The alignment also isn't perfect and there's some slight bleeding which I think could be caused by the temperature setting being too high. I've learnt a couple s few things from this. Next time I'm going to be more careful cleaning it, I'll a pencil to do touch ups and iron using a slightly lower temperature setting.

True a 9V battery with an open circuit voltage of 6V can't produce much current, however when the regulator is connected the open circuit voltage is unimportant. For example, suppose the battery is discharged to the point where its open circuit voltage is 7V but when you connect the transmitter, the voltage drops to 6V; if you were using an LM7805, the voltage to the oscillator will drop below 5V causing it to drift but if you used a LDO regulator, it would stay at 5V.

Is it possible? Yes. Is it easy? No. Sorry I'm not the bet person to help you with this.

The LM2936-5.0 will work down to 5.2V. The LM7805 will work down to about 6.5V with a low current load.

I thought every project you've built worked first time. :P

What preamplifier are you talking about? Please post a schematic?

You can use the LM78L05 if you like but the battery won't last as long.