Hero999

The first circuit seems to be the best one. Ideally the battery should be charged at a constant current until the voltage reaches 14.5V, then the current is stopped until the voltage falls to 13.8V at which point the charger can be switched to float mode which just regulates the voltage at 13.8V indefinitely so the batteries can safely be left connected without either overcharging or discharging.

No, this is the correct forum. You've not received any replies because you've asked a question then posted a link containing the answer.

Good for you for trying to repair an old CRT. Most people don't bother nowadays and use the opportunity to buy a brand new TFT flat screen monitor. Yes, you need higher voltage and current ratings and the frequency should ideally be higher too, although you should pay more attention to the switching times. I've never heard of VCESM or VCBO, only VCE and VCB, the former is the maximum allowable voltage between the collector and emitter and the latter is the maximum voltage rating between the base and the collector.

It sounds like the battery is flat so is unable to keep the voltage near 9V when a load is connected. The impedance of the battery rises as it discharges until it's so high, the voltage across the load is too low for it to work.

The 2SD2098 is available from Farnel, stock number: 1680155 http://uk.farnell.com/rohm/2sd2098t100r/transistor/dp/1680155?Ntt=2SD2098

The schematic is on the datasheet which can be found using Google. http://www.lmgtfy.com/?q=icL7107

It depends on where you live and the suppliers in your area.

It looks like you've made your choice but don't worry if you do change your mind later, it should be easy to undo the screws and reconnect the wires.

Yes, that will work, you can also use the LM337 to get a negative 1.25V to 10V. Here's a schematic to illustrate the point I made earlier. If the -12V pin is connected to 0V there will be a short circuit. An oscilloscope's metal case will be connected to the 0V pin.

That would work but it's probably more expensive and would be more sensitive to high voltage/current spikes. On the plus side, the contact life would be longer, it can switch faster and it's easeir to drive from the MCU. Take your pick.

It's pretty easy: use a transistor to drive the relay. There are 100s of examples on the Internet. You should learn how to use Google. http://www.google.co.uk/search?client=opera&rls=en&q=microcontroller+relay&sourceid=opera&ie=utf-8&oe=utf-8&channel=suggest http://www.instructables.com/id/How-to-control-a-DC-motor-to-run-in-both-direction/

It's generally very hard to find high-street shops which sell components these days, in any country and the small number of places that do are normally very expensive. The best solution is to go online. RS Components, Farnell and Digikey are the three largest international component distriibutors and a lot of part can be found on ebay but be careful of fakes.

I think he's talking about using the LM317 as a constant current source, in which case several LM317 current sources can be safely connected together than the currents will add together.

To measure the voltage between the ground terminal and protective earth, you should connect the meter between the ground terminal and the PSU's case or the ground/earth pin on the plug and make sure there's good continuity between the meter and the If the PC PSU's 0V terminal is connected to protective earth, it means the -12V rail will be -12V relative from protective earth. A typical oscilloscope has its chssis bonded to earth so if the -12V rail is connected to earth there will be a short circuit. If the PSU's 0V terminal is connected to earth, the LM317's output voltage will vary between -10.75V and 10V relative to earth. The output of the LM317 is only designed to source current. If the output is below 0V and is connected to 0V current will try to flow from the 0V rail into the regulator which will damage it. Remember that voltage measurements are relative, not absolute values.

You shouldn't need any fuses as long as the cable and terminal posts are rated to carry the full current. The PC PSU will be internally protected so short circuits shouldn't be a problem. I have three main concerns: 1) The power supply may need a minimum load current to give the correct output voltage. 2) The 0V rail of most PC power supplies is bonded to earth ground so the ground terminal of the 0 to 22V LM317 supply won't really be 0V but -12V which would cause a short circuit when you connect it to an oscilloscope and the LM317 will burn out, if the output voltage is set to < 0V its output is connected to real earth/ground. 3) Although you don't need any fuses to protect the power supply you might need a fuse to protect the circuit connected to it. It depends on what you're using it for, if it's just to power small MCU/logic circuits, it's prudent to have an output protected with a 1A fuse. You should also be aware that the LM317 can't provide 1.5A from 1.2V to 22V, you'll only be guaranteed the full 1.5A when the voltage is set to between 9V and 21V. Above 21V, the voltage might drop below the set value when the load is connected and below 9V the LM317 will reduce its output current to protect itself from overheating. This is all assuming the LM317 is on a really good heat sink.

What does blowby mean? At DC, the current through a coil is determined by the series resistance not the inductance. Whether the coil is damaged or not depends on the power dissipation (P = I2R) and its ability to dissipate heat.

I have read the datasheet. It's not a complete working inverter. It needs other components to make it work. You can't just wire it up and expect it to work. We need the complete circuit to help.

You forgot to post a schematic so there's no way any one can help.

Yes, follow the regulations which is different, depending on you location. Here in the UK you'll need a fused spur which is just a little box with a fuse inside it and is replaceable without switching off the main breaker. The cable run to the spur from the has to be the same size as the cable wired to the socket from the breaker and The cable to the light depends on the fuse in the spur which should be labelled. For a light, the 0.5mm2 will do and the fuse should be 3A.

The capacitance should be as low as possible because it slows it down and can cause resonance. Saturation is the point at which the iron core becomes saturated so an increase in current results in less of an increase in field. When core saturation occurs, the inductance drops to the point where the core is effectively not there.

In order to help you, we need a full schematic of your intended application.

Please provide more information.

You might get more help if you clearly state your requirements and said please rather than plzz which is just annoying to read.

LTSpice is good providing you have models for all te comopnents in the system.

How do you intend to produce the board? Are you going to be using the silk screen? If so, it's a total mess, the text overlaps the parts. If not, this doesn't matter, don't worry about it. There are some acid traps created by 90o angles but you've used such a thick trace width, it shouldn't matter.