Relay circuit

What have you go so far? Some simple logic? OR gates firing some one shot or 555 to give the one second. And an SR filp flop... Do you want the relay to close at the touch of a button, or only after the one second hold time? You could use old cmos 4000B series logic and run it all from 12V.

George H.

And are the switches on the ends of long wires in an electrically noisy environment, or all together?

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Tim Wescott 
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3 momentary switches and then operate a relay.

e been made for >1sec or the relay will not operate.

circuit

Hi- The device is to mimic a trigger for a competition that I help some school kids with. They have to design a robot that climbs a rope and it activates a plate at the top, triggering that it has made it. The robot has to push o n the plate for greater than 1 second in order to register. The pressure pl ate is round and each of the switches are located 120 degrees from each oth er. any one of them activates for greater than 1 second then it sets off a light signalling that the robot is stable and reached the top. I'm a mechan ical guy not electrical. My initial thought was just to put a latching rela y in but concerned that a quick bump on the switch would falsely indicate t he robot was "up". this whole set up is for testing our robot design. The a ctual competition has the real set up controlled by micro's etc. Was lookin g for a relatively basic solution that I could have some school kids help w ith. thanks for the assist.

Because you're a mechanical type I want to suggest something that uses a jackscrew on a gear-motor as the timing element for the 1-second delay. The challenge is to get it to automatically back off if it just gets blipped.

Because I've got a sense of humor. Or I'm evil. Or something.

This is Really Doable (with electronics), and if no one else helps out by tomorrow this time I will.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com 

I'm looking for work -- see my website!

. t t

thanks, their robot design uses a drum to winch in the rope which essential ly spools itself up into the pressure plate, not too far off your jack scre w joke. We are wrestling with just that issue of the robot impaling itself on the pressure plate assembly. Much appreciated on the circuit help.

f 3 momentary switches and then operate a relay.

ave been made for >1sec or the relay will not operate.

e circuit

l kids with. They have to design a robot that climbs a rope and it activate s a plate at the top, triggering that it has made it. The robot has to push on the plate for greater than 1 second in order to register. The pressure plate is round and each of the switches are located 120 degrees from each o ther. any one of them activates for greater than 1 second then it sets off a light signalling that the robot is stable and reached the top. I'm a mech anical guy not electrical. My initial thought was just to put a latching re lay in but concerned that a quick bump on the switch would falsely indicate the robot was "up". this whole set up is for testing our robot design. The actual competition has the real set up controlled by micro's etc. Was look ing for a relatively basic solution that I could have some school kids help with. thanks for the assist.

OK so you don't even need to drive a relay, just turn on an LED or somethin g. (and if the timing was a bit off would that be OK... 1.2 seconds say.) Do you have a 'scope that can be used to check the operation?

George H.

Our local "youth robotics club" is apparently in a similar competition.

Fine point: is the criteria ONE OF THE THREE SWITCHES must be pressed for a full second or, ANY OF THE THREE SWITCHES?

I.e., if switch 1 is pressed for 1/3 second then, just before it is released, switch 2 is sensed -- for perhaps 1/2 second -- and, finally, switch 3 (or, switch 1, again) for 1/6 second (1/3 + 1/2 + 1/6 = 1.0), is the goal considered met? Or, does *a* particular switch (any of the three) need to be HELD for a full second?

Essentially, you want the "switch closed criteria" (which may be three separate switch criteria) to enable a 1 second timer and, when/if the timer "times out", you want to set a latch indicating success. Presumably, you will manually reset the latch when the success has been noted.

[You probably also want to inhibit the robot's climbing power so it doesn't try to climb PAST (or THROUGH) the sensor array!] [[You'll also want to consider the actuating force necessary for the switches and how it relates to the "climbing force" of the robot; too stiff and the robot can "slip" as it tries to press against the actuating resistance]]

Yes, the robotics competition has teams from all over the USA and some inte rnational.

Yes, exactly correct. The switch closed criteria can be in any arrangement or order, they could be all in parallel as long as the total hold time is 1 second before the latch is set signalling success.

It does not need to be a relay could be darlington or whatever, prefer some thing with enough capacity to drive a light, prefer larger than simple LED so it could be seen from afar. Prefer to use what I have available which is spare 12V allen bradley signal light from the robot kit.

The creators of the competition have spec'd the pressure plate spring force to be 3 lbs. before it activates and total travel of the actuating plate 1 .5". Your comments are valued, think I've got decent handle on the plate an d robot, the electronics not so much.

In case you'd like to see what this is all about there is a video on youtube

at 2:20 they describe the assembly we are trying to mimic

I like your three switch idea, a simple way to make it work.

How accurate does the 1 second timeout need to be? If you use analog techniques the exact time value will depend on the tolerances of the components which can be significant, 10% from the capacitor before any temperature effects are considered. To get good precision and repeatability you might want to consider a small MCU which would be very simple to program for this.

--

Rick C

ternational.

t or order, they could be all in parallel as long as the total hold time is 1 second before the latch is set signalling success.

mething with enough capacity to drive a light, prefer larger than simple LE D so it could be seen from afar. Prefer to use what I have available which is spare 12V allen bradley signal light from the robot kit.

ce to be 3 lbs. before it activates and total travel of the actuating plate 1.5". Your comments are valued, think I've got decent handle on the plate and robot, the electronics not so much.

Connect the 3 switches in parallel. Their output feeds an RC that reaches 1 .2v in 1 second. Add a darlington with base resistor et voila, done. If the tr drives something inductive it'll need a diode.

NT

That won't really latch though at least not cleanly.

At the risk of groans for suggesting a 555 this might be closer to what the OP wants and is about as simple as it gets on strip board using a

555 aimed at Mechano engineers rather than electronics folk.

With the following modifications:

Move the switch on the RHS to the upper leg to switch the 10k resistor.

When the switch is pressed the capacitor will start to discharge until it reaches the trigger point or if the switch is made again then the cycle starts again. You might want to drop the 10k to 1k or 100R so that it is a start from scratch 1s if there is a momentary lapse.

Replace where the RHS switch is with a 10uF capacitor and 150k resistor in parallel which determines the delay time constant ~1s before the output latches on (adjust values to suit exact time delay required).

Reset side is unchanged. A 555 will drive about 300mA load. Modern LEDs are very bright so don't discount using one instead of the 12v light.

It will need a series resistor to limit current (or you could drive 3 LEDs in series with a smaller resistor).

--
Regards, 
Martin Brown

No, I somehow missed that. Just wire the relay to self-latch.

I suspect the problem is the OP wants us to do every little step of the process. There is no lack of options, and I doubt anyone here will explain every single point of every single step to someone.

NT

On 2/1/2017 1:14 PM, RKC wrote:

Here is a NE555 timer chip based approach. I looked at using a simple RC delay driving transistors and I don't think that will give you a stable and accurate timer. Here is a circuit based on the NE555 timer chip with many have come to love and hate.

The three switches are wired in parallel to 12 volts and the 555 Reset input with a 1 kohm pull down resistor to ground. This resistor is essential as the Reset input has an internal pull up. The 555 is held in reset keeping the cap discharged until any of the buttons are closed. Then the 555 comes out of reset and the capacitor starts charging. If the switch opens, the 555 is reset again and the cap is discharged at a much faster rate (roughly 10x). So switch bouncing will have little impact on operation, but if the device pushing the button lets off for even a tenth of a second, the timer pretty much starts over again.

When the capacitor charges to the threshold, the 555 chip output goes low and the capacitor starts discharging. To distinguish this state from the idle state, transistor Q1 acts as an AND gate combining the switch signal with the 555 output. When the 555 output is low and the switch signal is high Q1 pulls low drawing current through the relay coil closing the contacts for the output.

While the button is pushed the 555 timer actually free runs as an oscillator. To latch the time out state, the relay should have a second set of contacts (shown by RLY2) which will hold the relay in the activated state until a reset push button is pressed (not shown).

This circuit is simple enough it can be wired up on perf board using a DIP 555 chip and leaded components for the rest including the relay. A

12 volt power supply is shown. Add a 0.1 uF cap across the power and ground pins of the chip.

Here is an LTspice drawing to give you an idea of how the circuit should look.

Version 4 SHEET 1 1324 692 WIRE 336 -96 336 -144 WIRE -64 -16 -96 -16 WIRE 192 -16 192 -64 WIRE 192 -16 160 -16 WIRE 784 -16 784 -48 WIRE 784 -16 752 -16 WIRE 880 -16 784 -16 WIRE 752 0 752 -16 WIRE 928 0 928 -80 WIRE -656 16 -656 -32 WIRE -656 16 -800 16 WIRE -528 16 -656 16 WIRE -96 16 -96 -16 WIRE 880 16 880 -16 WIRE -800 48 -800 16 WIRE -656 48 -656 16 WIRE -528 48 -528 16 WIRE -64 48 -144 48 WIRE 272 48 160 48 WIRE 336 48 336 -16 WIRE 336 48 272 48 WIRE 336 80 336 48 WIRE -64 112 -176 112 WIRE 208 112 160 112 WIRE 272 112 208 112 WIRE 752 128 752 80 WIRE 816 128 752 128 WIRE 880 128 880 64 WIRE 880 128 816 128 WIRE 752 160 752 128 WIRE -800 176 -800 128 WIRE -656 176 -656 128 WIRE -656 176 -800 176 WIRE -528 176 -528 128 WIRE -528 176 -656 176 WIRE -432 176 -528 176 WIRE -240 176 -432 176 WIRE -64 176 -240 176 WIRE 208 176 160 176 WIRE 272 192 272 112 WIRE 336 192 336 160 WIRE 336 192 272 192 WIRE 928 192 928 80 WIRE 1072 192 928 192 WIRE 1120 192 1072 192 WIRE 336 208 336 192 WIRE 512 208 480 208 WIRE 640 208 592 208 WIRE 688 208 640 208 WIRE 1072 224 1072 192 WIRE -144 240 -144 48 WIRE 272 240 272 192 WIRE 272 240 -144 240 WIRE 208 256 208 176 WIRE -768 272 -816 272 WIRE -608 272 -768 272 WIRE -576 272 -608 272 WIRE 880 288 880 128 WIRE -816 304 -816 272 WIRE -576 304 -576 272 WIRE 336 304 336 272 WIRE 928 304 928 192 WIRE 208 336 208 320 WIRE 1072 368 1072 304 WIRE -240 384 -240 176 WIRE 480 384 480 208 WIRE 480 384 -240 384 WIRE -448 416 -448 400 WIRE -240 416 -240 384 WIRE 880 416 880 368 WIRE 928 416 928 352 WIRE 928 416 880 416 WIRE -816 432 -816 384 WIRE -576 432 -576 384 WIRE -576 432 -816 432 WIRE -176 432 -176 112 WIRE 96 432 -176 432 WIRE 752 432 752 256 WIRE 752 432 96 432 WIRE -576 448 -576 432 WIRE 880 448 880 416 WIRE -240 528 -240 496 FLAG 336 304 0 FLAG -96 16 0 FLAG -656 -32 VCC FLAG 336 -144 VCC FLAG 928 -80 VCC FLAG 1120 192 OUT FLAG 272 48 DIS FLAG -432 176 SW_INPUT FLAG 816 128 DRV FLAG 784 -48 VCC FLAG -448 320 VCC FLAG -768 272 CNTLP FLAG -608 272 CNTLN FLAG -448 416 0 FLAG -576 448 0 FLAG 1072 368 0 FLAG 208 112 THRS FLAG 192 -64 VCC FLAG 208 336 0 FLAG 96 432 OUT555 FLAG 640 208 EN FLAG -240 528 0 FLAG 880 448 0 SYMBOL csw -528 48 R0 SYMATTR InstName SW3 SYMATTR SpiceModel V1 SYMBOL polcap 320 208 R0 SYMATTR InstName C1

SYMBOL res 320 -112 R0 SYMATTR InstName R1 SYMATTR Value 91K SYMBOL res 608 192 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 1K SYMBOL sw 928 96 M180 SYMATTR InstName RLY1 SYMBOL voltage -816 288 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V1 SYMATTR Value PWL(0 1 1.99999 1 2 0 2.95 0 2.951 1 4 1 4.001 0 5.05 0

5.051 1) SYMBOL voltage -448 304 R0 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 12V SYMBOL res -560 400 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R11 SYMATTR Value 1000 SYMBOL res 1056 208 R0 SYMATTR InstName R5 SYMATTR Value 47K SYMBOL csw -800 48 R0 SYMATTR InstName SW1 SYMATTR SpiceModel V1 SYMBOL csw -656 48 R0 SYMATTR InstName SW2 SYMATTR SpiceModel V1 SYMBOL res 736 -16 R0 SYMATTR InstName R6 SYMATTR Value 200 SYMBOL Misc\\NE555 48 80 R0 SYMATTR InstName U1 SYMBOL res 320 64 R0 SYMATTR InstName R2 SYMATTR Value 1K SYMBOL cap 192 256 R0 SYMATTR InstName C2

SYMBOL npn 688 160 R0 SYMATTR InstName Q1 SYMBOL res -256 400 R0 SYMATTR InstName R3 SYMATTR Value 1K SYMBOL sw 880 384 R180 SYMATTR InstName RLY2 TEXT -754 -128 Left 2 !.tran 10S TEXT -752 -192 Left 2 !.model SW SW(Ron=.1 Roff=1Meg Vt=6 Vh=0 Lser=10mH Vser=0) TEXT -752 -160 Left 2 !.model CSW CSW(Ron=.1 Roff=1Meg It=-0.5m Ih=0

--

Rick C

seems like a good excuse to use a $5 arduino uno clone.

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OK. I didn't see that spelled out anywhere "formally". I just point it out as it can affect the timing and reliability of the "detector", esp if the robots are "wobbly" in their ascent.

To be clear: as this isn't being used *in* the robot (and, thus, not part of your formal entry) you aren't CONSTRAINED to this choice? I.e., if you wanted, you could wire a "Sonalert" (small device that sounds like a smoke detector sounding off) as the indicator...

And, you can run power or other stuff to the sensor -- which wouldn't be allowed during the competition. So, you could conceivably mount any electronics and/or indicators right above the "plate". As such, you aren't constrained to a small/cordless power source -- though that still may be preferable.

[Personally, I'd think a 9V "transistor battery" powering a Sonalert would be small, lightweight and "long-lived". Remove the battery when you're done for the day; replace it if it goes flat -- easier than dealing with a little power supply/wall wart that would require AC power nearby]

OK. Unfortunately, the actuating force doesn't reveal much about the quality of the switches used in the assembly. So, it is probably safe to assume they are "noisey" (i.e., don't have nice clean closures when they make/break)

More practical questions: what sort of "electronic" assembly skills and tools do you have? And, what access to parts/components? (I don't even think places like Radio Shack sell components any more)

Do you have a soldering "pencil" and know how to use it -- even if only crudely? Or, is your idea of a soldering iron one of those honking big Weller "guns" that you can use to solder lengths of rebar together? :>

Pencil:

Gun:

(Either can be used but the latter is far "coarser" in application)

Decent eyesight? Or, does the fine print in the phone book have you squinting? Likewise, steady hands?

Would you be comfortable attaching wires/components to a small (about the size of the fingernail on your littlest finger) integrated circuit? You need to be able to hold things steady enough for the solder to "set"...

The legs can be bent -- with care -- so you could bend some up, some down, to give you more room to work between them. The resulting "circuit" will be a bit fragile so, after verifying that it works, you could slip it into a "pill bottle" with the wires exiting through a hole in the cover (just to keep mechanical stresses off of the connections).

[For a more permanent solution, pump caulking compound into the bottle to encase everything. Of course, AFTER verifying operation as you'll never be able to "service" it, thereafter! Tip: this is a handy way of making waterproof connections underground, outdoors, etc.]

Alternatively, can any of your "kids" tackle this (no idea as to your age)?

See...

I'll leave it to you to add a Darlington or MSFET (2N7000 ?) to the output to drive whatever indicator you want.

I have presumed that "touching" for 0.9s and releasing and retouching resets to another full 1s required.

If "stumbling" contact is allowed, remove R3-R6, and Q1,Q2. ...Jim Thompson

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