A while ago, I bought a box of random surplus stuff and it had a big stack of these circuit boards in it. The only marking on the board is ‘IN CAR 001’, which might give us a clue, but we’ll get back to that…
OK, looking at the track side of the board, it’s clear there are four distinct channels of operation, terminating in a bunch of screw terminals at the top end of the board; immediately facing the larger row of terminals are four sets of what appear to be power transistors or similar; because of their spacing, I can only read the designation on the front ones, which say MTP3055A, anyway, I’d say that must be the output stage…
Immediately below them are four rows of smaller transistors; 2N7000’s; I assume this is some kind of amplification or switching stage.
On the other end of the component side, there are some ICs - HCF4049 (Hex buffer/converter), HCF4024 (Binary ripple counter), GD4093 (some logic gate chip, I think), SI7661 (voltage converter), plus a load of resistors and a few other transistors dotted about.
Now, I’m sure it would be quite possible to trace a complete layout of this circuit and deduce the precise nature of its function that way, but I can’t escape the temptation to work it out by ‘feel’ - the thing looks like a motor controller of some kind, but the inputs (Just power, ground and one signal line) and the outputs (just four pairs of output lines) seem to rule out a stepper motor controller or even a motor speed controller.
My best guess at the moment, based on the layoiut, the inputs/outputs, the kind of components, the four channels and the name ‘In Car 001’ (and In Car Systems’ on some other devices that were in the surplus box) is that we’re looking at an after-market vehicle central locking controller board.
Anyone care to agree/diasagree/speculate?