Possibly OT but anyone know anything about and ideally where to get an old style petrol attendant "sevice" bell ? (the bit of black rubber hose? that you used to see stretched out across the garage forecourts - when your wheels went over it it rang a bell in the office to alert the pump attendant to your presence....)
ta Jim
jim coughed up some electrons that declared:
You could probably make one - all you'd need is some rubber pipe and a pressure switch (something from RS or Farnell, or even a washing machine water level switch (air pipe into water type) is probably in the right sort of range.
Cheers
Tim
If you're going to operate an electric bell from the pressure sensor line then another source is air pressure switches from many boilers, often available as scrap. However it would be neat to have the air pressure ring the bell directly, which would require a bit more ingenuity.
yup, it is an amazingly simple devise, i used to work at a self service garage that had this set up,
The hose was special soft easily colapsable hose, and used to split after about 6 months use, it was more of a sponge rubber,
the ends were knotted, i guess at one time proper plugs or caps would have been used, the other ends went into the old car show room into the electric cupboard, where the hose was pushed onto a pressure switch, about the size of a tea cup, was a diaphram inside, spring loaded with an adjustment screw in the middle, the slight pressure wave of a vehicle driving over the hose dperessed the diaphram, and the switch rang the bell,
unfortunately at that place they used a 'rrrriiiiinnnggggg' type door bell, which was fine if cars ran over it, it's go 'ding ding' but when the trucks came to fill up one of hteir trailer tyres would be on the hose, and the damn bell would ring all the time.
Also had to adjust the sensativety of the switch every few days if the weather changed a lot, but half of that was down to them trying to use normal pvc hose which sent a much lower pressure wave to the switch as it didnt crush much.
gazz coughed up some electrons that declared:
That sounds about the same form factor as a washing machine level sensor.
Do you remember when traffic lights had this sort of setup, with two hoses set into the road?
i'm not that old, this was in about 1995... prolly one of the last remaining full attendant service petrol stations around, and was only self service because the boss was too tight to get new pumps that could be controlled from inside, hence it had to be attendant service by law as no way to shut the pump off if someone did something silly with it.
They were called road pad detectors.
Originally they used a pair of sprung steel plates held apart along the edge, which deform and make contact with vehicle weight (but supposedly, not by jumping on it). A twin version allowed detecting direction of traffic, but was often used because when one unit broke, the controller could be connected to the other one until they could be replaced, which was required on a routine basis.
There were a number of attempts by the likes of GEC and probably Plessey too to come up with longer lasting inserts for the iron holders, and I did see pressure tubes.
Inductive loops have taken over now of course, and they work with cyclists too.
inductive loops eh... could you describe how they work please? - are they DIY-able?
ta Jim
inductive loops eh... could you describe how they work please? - are they DIY-able?
ta Jim
A sort of up-side down metal detector, i.e. the metal detector is buried in the ground and detects metal passing overhead. Google is you want to know more.
Yes, but possibly not legally. I don't know what the radio licence requirements are, but whatever, you're unlikely to have the tools necessary to prove they meet the radio licence requirements (as they are radio transmitters).
Since when did the state of a traffic light matter to a cyclist? ;-)
jim coughed up some electrons that declared:
Have a hunt around on google for metal detector circuits and try Elektor magazine.
Alas you'll have to buy a subscription to actually read these, but:
Well, _I_ still obey them as a cyclist, although I admit that I'm in a vanishing minority, along with wearing reflective materials and having working lights.
Doesn't matter to them at all, they don't contribute towards them, scrounging gits.
BTW - did you know that MP's can claim 20p per mile for travelling by bicycle?
You couldn't make it up could you?
IIRC below a certain level of emission you dont need any license or approval. Cant remember what power that is though, but its a small fraction of a watt, and doesnt trasmit far.
NT
So can anyone.
Got to keep Dave and Boris happy! But any business can pay an employee 20p per mile for using a cycle. This will be an allowable business expense set against tax and tax free to the recipient.
I'm 200' above sea level! Never get back up Watling Street!
Not really, they are inductors. The inductance of a loop changes when a piece of iron (and some other) materials pass close by. If the inductor (the coil buried in the road) is in a tuned circuit then some characteristic of that circuit can be used to detect when the inductance changes. There are no radio emissions, it's just electromagnetism.
See, for instance:
R. (who used to work for GEC-Elliott Traffic Automation, back before the flood)
In the context of the OP's question e.g. a garage bell, perhaps the signal could be transmitted with a wire?
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