| oops,
Now going backwards, I haven't got that much of a choice of resistors at home so I used what I had, firstly I went for bigger voltage pulse to the tacho, this gave no reading at all.
So I then went the other way so I had about a 3 volt pulse going to the tacho, this caused the engine to run poorly, the tacho needle to jump about and then after about 30secs fried the chip in my circuit and melted the base it was plugged in to.
It looks like the original voltage of 6v was the closest and it may be the pulse length that is the reason the readings were falling short of what I expected.
Prototype 2 is now at the design stage, but I doubt if it will progress much over the weekend due to a lack of componts at home. |