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Author Topic: 1.2 volt relay? or something to do the same job.  (Read 1405 times)

Andy M

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1.2 volt relay? or something to do the same job.
« on: June 09, 2019, 11:07:17 PM »

Hi, I was wondering if any electronics geniuses know what I could use for my latest project. I have a solar powered led light which I want to use to connect two contacts on a stopwatch. When the solar panel is in darkness, the led comes on, I would like to use the 1.2 v output to connect the 2 stopwatch contacts. A relay seemed the obvious choice but I cant find any 1.2v relays, non latching. Can anybody suggest either a suitable relay or some other way of doing the same thing? Many thanks in advance, Andy M
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grendel

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DaveM

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Re: 1.2 volt relay? or something to do the same job.
« Reply #2 on: June 10, 2019, 09:41:29 AM »

I would suggest a light-operated switch, running from a separate power supply and activated by the LED. There are any number of circuits for these on the Internet.
DaveM
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grendel

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Re: 1.2 volt relay? or something to do the same job.
« Reply #3 on: June 10, 2019, 12:13:56 PM »

if you just want to trigger a pulse a simple flip-flop circuit would suffice.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #4 on: June 11, 2019, 11:29:52 AM »

Hi, thanks for your answers, first of all the relay was a bit over my price range, I was hoping to recycle a component(s) if possible, its for the environment, not because I am scottish.Honest. The light operated switch sounds promising, I wondered if another solar light could be modified to do the job somehow. I have no idea what a flip flop is, but a pulse should be enough to start the stopwatch I would think,  what components would I need? Andy
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #5 on: June 11, 2019, 11:37:28 AM »

Will the flip flop circuit keep the 1.2v from solar light isolated from the 3v of the stopwatch contacts? Thats why I thought a relay would be best. Andy
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grendel

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Re: 1.2 volt relay? or something to do the same job.
« Reply #6 on: June 11, 2019, 11:45:28 AM »

a flip flop circuit is basically a circuit with 2 transistors
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #7 on: June 11, 2019, 03:09:34 PM »

Does the reset button have to be pressed to disconnect the stopwatch circuit, really I only want a momentary contact to activate the stopwatch and then connect again(momentarily) the next time the led (1.2v ) comes on. I should really have explained fully what I am doing, I have a home made race track and cars and want to time a single car lap time, as it crosses the line. I have a separately powered led in a tube to direct the beam and the solar powered light with its solar panel on the opposite wall of the track, it works perfectly, the solar light led flashes as the car passes between them, even at speed, so this bit of it is exactly as I want  (would really like full transponder setup in every car but too expensive) I need to be able to use that short pulse to connect the two contact wires I have added onto my stopwatch, which have 3v over them. Hope that clarifies it a bit. Andy
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #8 on: June 11, 2019, 03:14:05 PM »

 I thought I should add that I build boats too, several are shown on mayhem, a while ago, I hope to show my little race cars on the other hobbies section as soon as I get some photos down to the right size file.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #9 on: June 11, 2019, 03:40:24 PM »

Here are our cars on the grid, 1/27 scale with mini body basically a half scale mardave ministock. Shells are made from ice cream tub lids. Four of us have them now, best rc cars I ever had/made. Lego tyres on home made wheels, my car has done over 1000 actual miles! They do about a mile on a charge, 20+ minutes running time.
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grendel

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Re: 1.2 volt relay? or something to do the same job.
« Reply #10 on: June 11, 2019, 07:18:56 PM »

basically the addittion of a capacitor to one side means it flops back automatically, sort of half of a multivibrator circuit.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #11 on: June 11, 2019, 07:48:15 PM »

Could you tell me which transistors, etc I need? And where they go in relation to the diagram. I take it the switched contacts to the stopwatch are on the right? And there is no voltage on them, and they can take the 3v from the stopwatch contacts? Sorry for all the questions but I was never very good with electronics, managed a few things over the years but its still a black art to me. Many thanks for your help.
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coch y bonddu

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Re: 1.2 volt relay? or something to do the same job.
« Reply #12 on: June 11, 2019, 08:43:44 PM »

Definatly INTERESTED in this big time Andy M this is mine




61002001_826992794366103_1150081805374717952_n by David Jones, on Flickr

Full build one here

https://www.slotforum.com/forums/index.php?showtopic=189239


Dave
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malcolmfrary

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Re: 1.2 volt relay? or something to do the same job.
« Reply #13 on: June 11, 2019, 09:28:03 PM »

If all that is needed is something to spot when the red light is obscured by a passing car for the time that the car is passing in order join two connections together, a phototransistor (google is good at this) will do the sensing.  If one of the two connections is at ground, and the other is positive, a small switching transistor will do the job of looking at the voltage around the phottransistor and shorting the two connections together while the light is obscured.  If that describes the job, sorting a circuit and settling component values becomes relatiyely easy.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #14 on: June 12, 2019, 12:16:45 PM »

Here is what I have so far. I am pretty sure that the 1.2v solar side shouldnt come in contact with the 3v of the stopwatch. But I could be wrong.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #15 on: June 12, 2019, 12:21:30 PM »

Here is my full track, even has access tunnel underneath. Lol. Got to crawl under. Cars are 1/27 scale, scalextric car shown for size comparison.
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grendel

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Re: 1.2 volt relay? or something to do the same job.
« Reply #16 on: June 12, 2019, 12:35:55 PM »

I think the basic circuit you need is something like this, using an IR diode and detector (another diode) and just getting the cars to split the beam
https://www.youtube.com/watch?v=qEMtCKfZOHw
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grendel

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Re: 1.2 volt relay? or something to do the same job.
« Reply #17 on: June 12, 2019, 12:50:20 PM »

You used to be able to find wiring diagrams for these simple circuits in the past, but nowadays they complicate everything by running them through computer circuits (arduino) to make everything simple, somewhere at home I may have an old electronics kit that has the type of circuit you would need for this in the instructions, but its a matter of finding it.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #18 on: June 12, 2019, 01:39:52 PM »

If you could find it, that would be good, would it detect over a 14 inch gap, (track width)? I do have an old pir sensor, am I right in assuming it would have the i.r. emmitter and detector ?

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clockworks

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Re: 1.2 volt relay? or something to do the same job.
« Reply #19 on: June 12, 2019, 01:51:56 PM »

I built a timing and lap counting setup for a slot car club a few years ago. I used IR LEDs in an overhead gantry, and IR sensors fitted into holes in the track. I also built start countdown lights (F1 style).  The sensors and lights were run from the parallel port of an old laptop, and the software displayed lap times and race positions in real time. Unfortunately I'm not a member of the club anymore, and I can't remember the name of the software. I think it was either free or very cheap.


Before settling on the above/below IR method, I tried visible light (too much interference from ambient lighting), bouncing IR off a strip of metal tape under the cars, and reed switches to detect magnets on the cars.  IR was pretty much perfect, although we had to switch off the high-level radiant heaters in the hall during each race.


A bit harder to do for a small RC track like yours, as the cars don't stick to individual lanes, but I think you only want to time one car at a time?
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #20 on: June 12, 2019, 03:16:25 PM »

It would be amazing to time all four cars at once, but I know thats going to be much more expensive than I can afford. Being able to time just one car will be good enough for now. Maybe my shed is very dim, I was getting consistent operationof the led on solar light, even when I covered the top half of the solar panel with black tape as it was detecting through the windows of the cars. Now the bottom half of the car going through beam activates the led.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #21 on: June 12, 2019, 03:24:58 PM »

I have started a topic on the other hobbies and interests section of the forum showing my cars, track and how I came to build them. I will show how I converted the cars if there is enough interest. The donor cars need modifying, some of it quite fiddley, but you end up with an awesomely fast and tough little race car that does 20 minutes at our race speeds.
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malcolmfrary

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Re: 1.2 volt relay? or something to do the same job.
« Reply #22 on: June 13, 2019, 10:11:54 AM »

Ditch the solar panel, control board and LED.  Use the circuit linked to in post #16, or at least everything on it except the light source diode which you already have.  Use the output of the Op-amp to drive a relay, use the relay contacts to operate the stopwatch.
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Andy M

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Re: 1.2 volt relay? or something to do the same job.
« Reply #23 on: June 13, 2019, 01:04:27 PM »

Is this suitable ?
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RST

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Re: 1.2 volt relay? or something to do the same job.
« Reply #24 on: June 13, 2019, 06:43:48 PM »

Cool little cars on 'tother thread. Have a look for velleman kits. They do a PIR light gate which might be of use. Shame maplins has gone for these little projects.
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