I have a automatic steel shooting target, when you shoot the steel the target falls and is reset by a battery and motor. To keep the motor from continuously running there are 2 magnetic proximity sensors. One to detect the target down - start motor, and one to detect target up - stop motor. Right now the part of the card that senses target up - stop motor, sometimes fails to stop the motor. The sensor tests out and even the company knows about the problem, because they have changed the board and secured it better. They want 125.00 for the new card, can a new card be made and programmed for less?
Second - they have a radio control upgrade, different card, addition of a knock down motor or actuator, Antenna, and ?? for 700.00. Plus shipping the target to them and back to me (weighs about 120lbs). Can it be done for less and still operate on the 1000 meter distance?

 

Unfortunately you sound like you are talking about a one-off design. Unless the card is extremely simple (which is possible) and you can identify all of the components on it and trace out the circuitry, you would need to reverse engineer the functionality and the interface requirements to the rest of the system. Since you mentioned programming, you would need to also design a suitable program. I don't know how much your time is worth to you, but even at $10/hr you could only justify a day or two of effort before your time chewed up the $125 before you even bought a single component. Unless you are prepared (and already set up) to manufacture your own printed circuit boards, that is going to dig into your budget as well.

Similar for the radio control system. If you have to design the system, then how much time can you devote to it before you would have been better off delivering pizza for two or three weeks to get the money to buy it?

Now, if your time is of no value to you in this instance, perhaps because you want to learn how to do these things, then that is a very different situation. But if you are starting from scratch you have a fair amount to learn, it will probably take you quite a while (especially for the remote system) and you may still spend more than those price tags when everything is said and done if you aren't careful.

 

The first question is what is your skill level? I'm presuming fairly low or you wouldn't have asked the questions you did.

One of the the things you (in theory) are paying for is the engineering needed to make something like this reliable. It sounds like it isn't very reliable so perhaps you aren't getting enough value for your money. It's relatively easy to put something together that will have "make magazine" reliability but over the long run that kind of stuff eventually needs tinkering to keep working. Especially true when there are forces involved like bullets hitting a steel plate. Can you do better than the company that makes it?