Hello Ron, thank you again for your reply – it is very much appreciated.
I take your point with R1 / C4. I think they may have been left over from some failed attempt to do something many moons ago and I was too frightened to remove them just in case I broke something! This is yet another example of my lack of knowledge letting me down. I have remove them and all is fine – Thank you. (Please see new diagram).
Again, you have guessed where I was coming from. My plan is to use a variable resistor to control the buzzing frequency. Basically, I am trying to create a timer alarm for my father who is getting on in years and needs to take an extraordinary amount of tablets at different times. By marking around the pot, the time intervals that he requires, he can (hopefully) just move the dial and press the button. He did have an alarm clock with four times, but he needs more than four and could not successfully change the alarm with changing the actual time or doing something else that would mess up the system. One of his major ailments is that he has renal (kidney) failure. This requires him to have a bag of fluid drained from him and new bag put back (basically, the fluid does the same job as the kidneys). I want to use the LEDs to signify how long he has until the next lot of medication so he can plan his time. However, as the first prototype, I was thinking to just making a food times of something that I could test accuracy.
I have taken your advice and used a transistor to boost the current going the buzzer. This is a basic electronics question – when playing the value of R4 I noticed that the higher resistance I used, the smaller the amps, the higher the voltage. Is this common behaviour for a transistor or is this just the way in which I have implemented the design? If so, does that mean that it is always a trade-off voltage and current? Also, by putting a resistor (R3) before the pot, will that be the lowest resistance charging C1 – if VR1 (100K) was turned down the 0% then do I have 10K feeding C1, if VR1 was 100%, would I be charging C1 through 110K resistance?
Again, I would like to thank you for your time and effort.
Kind Regards,
Harold Clements