Model Boat Mayhem
Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: Andy M on June 09, 2019, 11:07:17 pm
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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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https://www.ebay.com/itm/PS7113L-2A-A-NEC-SSR-Relay-SPST-200mA-1-2V-DC-In-0-400V-AC-DC-Out-8-PDIP-NO-/192848545004
something like this?
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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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if you just want to trigger a pulse a simple flip-flop circuit would suffice.
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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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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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a flip flop circuit is basically a circuit with 2 transistors
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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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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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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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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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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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Definatly INTERESTED in this big time Andy M this is mine
(https://live.staticflickr.com/65535/47925531681_d35c4f29a3_c.jpg) (https://flic.kr/p/2g21SSn)61002001_826992794366103_1150081805374717952_n (https://flic.kr/p/2g21SSn) by David Jones (https://www.flickr.com/photos/166794344@N07/), on Flickr
Full build one here
https://www.slotforum.com/forums/index.php?showtopic=189239 (https://www.slotforum.com/forums/index.php?showtopic=189239)
Dave
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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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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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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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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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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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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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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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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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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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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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Is this suitable ?
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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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Googled it but the kit never showed in the results? Dont have a number for it do you?
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MK120 from a google search. On phone so links are hopeless am afraid. May not be any good but I can't download the pdf manual at the moment to check myself. Before anyone else says, no doubt you can import a Chinese copy for pennies, but I've used velleman etc kits before and they're ok for the money.
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Hi , had a look, it says range of 1-4metres. I need 0-35 cm. I dont know if that means it wont work on my set up. Doesnt mention whether its a momentary action or if it stays on.
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The kits pictured will very nearly do the job. Their task is to switch on when they see light, off when they don't. Using a relay, and a non-battery supply, the relay can be permanently operated, releasing to the dark. Or the sense pot and sense device can be transposed.
The drawing (found on the internet) shows the modification to change it to operate the relay when it loses sight of the light source.
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Hi, sorry not replied sooner, wondered what rl was and also I assume vr is variable resistor? Excuse my ignorance.
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Hi , had a look, it says range of 1-4metres. I need 0-35 cm. I dont know if that means it wont work on my set up. Doesnt mention whether its a momentary action or if it stays on.
Hi Andy, sorry red herring I think. The info available for it is pretty pap also.
Rich
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Hi, sorry not replied sooner, wondered what rl was and also I assume vr is variable resistor? Excuse my ignorance.
Yes, VR has been the standard shorthand on diarams for variable resistance for a while, and while relays get a lot of different names, especially in circuits with a lot of relays, this one at least says " relay" alongside it.
Any of the kits should come with a diagram, but most switch the relay on when light falls on the sense element. The application here requires that, unless the relay is permanently operated until the light beam is interrupted, the logic will need to be inverted somewhere along the line. Having the sensor (which goes to a low resistance state when lit up) switch the 1st transistor off by shorting the base to emitter rather than applying a reducing resitance to the base to switch the transistor on, is the easiest way. This does mean that the variable resistor needs a bit of padding to ensure that current via the base is limted whatever the setting of VR.