cliff park

Press buttons, ie momentary , not switches

Surely the simple way would be a relay, with changeover contacts such that when operated controller A is connected, when released controller B. Then each operator has a button. Operator in position A is a make button and operates the relay, which then holds over a spare contact. Operator's B has a break button which releases the relay. Another spare contact could be used to light appropriate LEDs.

Slightly off topic. My Dad was a carpenter and was over the moon when PVA glue appeared on the scene, after a lifetime of preparing scotch glue. He used to dilute the PVA with water in a jamjar and one night he went to bed leaving a residue of diluted glue, and an old tablespoon in the jar on his sawbench. The next day he had to smash the jamjar to get the spoon out, then chisel the remains of the jar off his sawbench. The point is PVA is much more useful than you may realise, even diluted.

Heaven is in the back seat of my Cadillac - Hot Chocolate

Also what sort of level are your woodworking and electrical skills, and what access do you have to machinery , tools etc ?

I recently bought Draper's temperature controlled iron and am very happy with that. I agree fully with junctionmad's comments as well.

Fitting some LED interior building lighting I was looking for some very fine wire and remembered varnished wire. I am talking about the sort used in motors, solenoids, relays, even loudspeaker coils. The picture below is of the mechanism from an extension telephone bell. It looks like bare wire, but is of course varnished otherwise the turns would be short circuited. The varnish is actually the biggest problem. It is surprisingly difficult to remove. I use a small piece of fine sandpaper or emery cloth gripped between finger and thumb and drag the end of the wire through it. It must be removed before the wire can be soldered. The varnish does not take paint particularly well either. The picture below shows an LED powered by the two wires which are threaded through the eye of a needle (don't tell the wife I borrowed it). OK it is a darning needle, but still a small space. This wire, from the coil above measures 0.3 mm according to my vernier. In case you feel it can't take much current remember that motors, solenoids etc take quite a hefty current, and with only varnish for insulation there is no fear of it overheating. (Excuse the crude wiring, all done in a bit of a rush). So don't throw away your old solenoids, motors etc, strip them down and have a play.

I think the mF on the diagram means μF, ie microfarad. So 4700μF would be correct

The standard with fuses is that they blow at twice the rated current (don't ask me why) and will carry near to that value forever. They will get warm, maybe even hot, but not blow until twice the rated current. I have had plugs get hot, even good old MK, if the wires are loose or poorly terminated. eg only one or two of the cores actually terminated, or the screws not really tight. It does pay to go round your house about once a year and check all the screws and terminations where you can get to them , particularly those carrying heavy current like heaters, kettles, immersion heaters, washing machines, dishwashers, tumble driers etc. (And there will be an awful lot of them)

If the voltage is too high don't forget the simple option of half wave rectification. In other words one diode in series with one of the supply leads, and forget the bridge rectifier. It may work better with a bigger capacitor, depending on how much current the LED's draw.

This is akin to a magician telling us how the trick was done and spoiling the illusion.

One problem with all of these calculators is that they don't take account of 'preferred values'. In other words if the calculation says '395 Ω' then the modeller tries to buy one he will come unstuck. Always go up to the next preferred value, and if in doubt start high, if it's too dim come down. Unless you are feeding a lot, or they are very high powered, a ¼ watt should always be adequate. Several companies sell a selection pack fairly cheap, they always come in handy.

In essence it is as you describe. And if it goes wrong it can cost several hundred pounds to put right, ask me how I know. They would not be feasable on solenoids anyway, and it is probably possible to adjust voltages on any other motors, including servos, to achieve a similar effect.

Don't forget that asbestos is fine until you break it, saw it, drill it etc. The elements in these kinds of devices were usually ceramic, not asbestos. I know they look similar, butI have never seen an element with asbestos in it .

The danger with soldering anything where the wire may move is that the wire will break, or at least individual cores will, where it goes from soldered to not-soldered. If soldering a wire which is then going into some form of screw terminal or similar, fix the wire so it cannot move about. An alternative is heat shrink from the soldered part to some way down the unsoldered. This means any flexing is in the unsoldered, flexible length.

It is possible to use bolts, 'crimp' the socket bit slightly to make the sliding part a good fit, BUT arrange the bolt to operate a microwsitch, such that the switch is only operated once the bolt is fully inserted. That way the only live track is the one lined up.

Have you tried filing the end of the brush dead flat, ie so it is not concave. A smooth file should do it, but gently, carbon is soft. It should still make enough contact to run the motor, and then bed back in. Also check for end float of the shaft to make sure that the thrust is not pushing it along so that the ends of the windings are touching the brushes.

One of the difficulties of using a resistor is that the current drawn by the motor (and hence any volt drop across a fixed resistor) will vary, quite considerably with load. If the load is reasonably constant the best way would be to measure the current, and use that value to calculate a suitable resistor. I suspect it will be low value, a few ohms, but will need to have a large power rating. A much better way would be, as I think you suspected, to have a supply of the correct voltage to start with. You could add a variable voltage supply ( ie a good old fashioned DC train controller ) in series with your 12 volt supply, giving you a voltage variable between 12 and 24 approximately. You could then measure the voltage which gives you the speed you want, then 'organise' a supply of that voltage.

This may be obvious, but just in case:- if measuring voltage put one probe on each 'leg' or wire. If measuring current you must connect the meter in series, ie disconnect a wire and connect the meter in place of it. When measuring resistance the circuit must be switched off, ie no power. With a digital meter polarity is irrelevant,it will show a negative if the wrong way round. If measuring a varying voltaage digital meters can be difficult because of the sample rate

A couple of small points:- the nosebag would have contained oats and/or mash, hay in a bag that size would last about 10 seconds, the blinkers became much more common as more and more motorised vehicles came on the scene, to stop the horses being spooked by them.

If you start with 1000 ohm ( 1K ) resistor in series with any LED you won't go far wrong. If it looks too bright try a 1.2 K or a 1.8 K ( 'preferred' values ), if not bright enough try 820 Ohms or 680. As regards polarity, look carefully at the body of the LED, most have a flat on one side, and/or one leg (wire) longer than the other. But don't panic. With the resistor in series and a 9-15 volt, dc supply it will light one way round and not the other, but it won't do any harm. It just won't light. Make a note which way is right for your particular LEDs

Strangely in the shot with the tripod it looks as if the driver is looking at it, perhaps wondering what it is doing there.............

Use a low voltage source, say 5v, and a 1k resistor in series. Make careful notes of which way round you connect positive and negative and try it. If it lights up it is the right way round, if not reverse it. It won't do any harm, it just won't work the wrong way

Does the input go into a bridge rectifier, either a one-piece affair or 4 diodes, maybe in a square ? Can you show a picture of the component side of the board where the input leads are connected.

I think the listing is caused by the angle the photograph was taken.