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Just checked the site out of curiosity and looked at the Tracker, TT5. It has faults on it - I wonder if this is typical of the other circuits?

If it’s not too late to change direction, have you considered going down the switch-mode route? My ageing 28V 2A power supply (using 2N3055) is now getting past its ‘sell-by’ date, so I intend to make a new one using ready made inexpensive modules from ebay. I already have an HP laptop power supply that delivers 18.5V at 3.5A. That will power a buck converter to give an adjustable output of 1.8V to 16V at up to 5A (subject to the 65W maximum of the power supply). The buck converter module has two presets to adjust the output voltage and the current limit. I shall replace these with normal pots. The output voltage and current will be displayed on two 3digit LED displays – again using ready-made modules. To get a higher voltage, when needed, I shall switch in (between the power supply and the buck converter) a boost converter that can give up to 32V output at up to 3A. That will then give me an output of 1.8V to 30V. I’m waiting for the displays to arrive at the moment, then I’ll start hooking it together. If you are interested in making something similar, I can give you the ebay item numbers.

It seems logical to eliminate the welder transformer if you can and connect the micro tranny straight to the mains. There are plenty of ways of making a spot welder from one. Go to Youtube and look for 'Spot welders'

How about a robotic lawn mower?

You could use a micro to send 3 bytes of data every 5 seconds via a small Tx like those from RF Solutions. That would give you almost 17million combinations of code. By the time you got on to your bike the Rx would have received the code and disarmed the bike. If it received no further codes in, say, 10secs the bike would be re-armed.

You are splitting hairs. Audioguru is right. Base current is controlled by the value of the base bias resistor. Current through the base emitter junction will cause a collector current equal to base current times beta. Both of those currents will flow through the emitter. It makes no difference whether the device is NPN or PNP.

Try this link. The info you need is towards the bottom of the page. http://pinouts.ru/data/Serial9_pinout.shtml

Hi Windoze, Here's an op-amp which may do you. It goes rail-to-rail on its input and output. http://www.datasheetarchive.com/search.php?search=lt1782&sType=part I'd like be interested in your final solution when you get it all going. Best of luck.

I have read them, so what have I missed? Please read my PM.

I cannot see how this more complex arrangement is better than Staigen's proposal in his post #6. Or have I missed something?

This is a very good link to batteries. http://www.batteryuniversity.com/parttwo-33.htm

Now you have said what the purpose of the project is, could I suggest an alternative? How about a dedicated micro just for this data input. Input would be to the A/D convertor section of this micro reading the 2.5v to 5v. Compare the digital readings obtained with a lookup table that will give equivalent outputs in the range 0v to 5v. Then output that to an R2R ladder network to give D/A to go into your main micro. You can still use just the 5v supply.

Hi Staigen and Enac, You are both right. With input=5v, inv input=5v, output =5v and no current flows through the resistors. With input = 2.5v, inv input=2.5v, output=0v because current flows through both resistors and giving equal voltage drop across each. So inv input is 2.5v below +rail (5v), and output is 2.5v below inv input. EdwardM, Your circuit is flawed because with R1=R2, the LH side of R3 is effectively sourced from 2.5v When input=2.5v, inv input must be at 2.5v. So no current flows through R3 or R4 and output will be 2.5, whereas it should be 0v Windoza, This is such a simple circuit it cannot possibly fail. If you are still having trouble simulating it then either the simulator is handling the parameters of the opamp incorrectly, or it is selecting the wrong opamp. I cannot beleive the simulator has a fault - but worst things have happened. Don't mess about with the simulator - just build it. It will work!

They use their timer to measure the time between two interrupts, then calculate the RMP from that.

Even if the Altium isn't simulating with a rail-to-rail op-amp, it should give results that are pretty close. I've not used the package so I don't know. I would try it for real.

I gave you the same answer as Staigen's on another forum. Trust him. It will work!