Decade Resistance Boxes

Discussion in 'Supporting Physics' started by Nick Mitchener, Aug 8, 2018.

  1. When the requirement appeared for these in the OCR PAG on sensor circuits I seemed to be the only one in School who knew what they were.

    We couldn't afford to buy new so I hunted about and came up with a way of making them that would not cost too much and wouldn't take up loads of space for something we don't use much.

    Although I'm TTO I ran out of time to make more for the larger classes this coming year so I've made them at home. While I was at it I took pics along the way and I've knocked up an instruction sheet if you want to make them too.

    These ones work out about £12 each I think, but you can make them with more decades if you want or different values. I chose these values as they work well with out thermistors which are about 23kr at room temperature. I chose the minimum of 100 ohm so that if I only g ave the little darlings 5/6 volts they couldn't burn them out.

    https://docs.google.com/document/d/1Vh3GIvHg9lCOkIithp4a1PFI06Fo9RBuP-odqVIaiP4/edit
     
    John j likes this.
  2. Dod

    Dod

    Nice ones Nick.

    We are fortunate that there are 3 ancient very dusty ones in our store.
     
  3. Great work Nick. I didn't know these 'wheels' existed. I think half the battle is knowing what's available out there.

    We do OCR A-level, but not the sensor experiment. As it happens, we're fortunate to have quite a few resistance boxes. They do get occasional use, particularly when we're looking at capacitors and time constants. We also have a number of decade capacitance boxes.
     
  4. I have found whenever I pick up an old decade box that has been used by little darlings they have burned out some of the lower values. When I give these out I only give them supplies that are limited to 5V. Now we are having bigger groups I will give them battery packs.

    I found wheels being used in an instructable and modified it to suit what we wanted and what wheels I could buy.
     
  5. Fair point re the lower value resistors. I'll check ours.

    Good old 'Instructables'. Mine of useful stuff.
     

  6. Without google I would be lost.