boe relay question

firealarmfreak

hey i just got an idea for power supervision and i want your input on whether you think will work.

If i were to get a 12 volt dc relay and a 12 volt dc adapater---connect the 12 volt dc adapter to the relay coil---connect the normally closed portion to one side of the boes power, and the common to the other side of the boes power---and then connect an led to the normally open portion, the other side to a seperate 3 vold power source---and the other side of that power source to common (or something like that), would the led turn on when the relay turned off?


What i understand will happen is---when the relay is turned on--the relay will apply power to the boe (board of education), through the normally closed portion. But when the relay loses power and turns off, the relay will turn on the normally open portion, causing the led to turn on.

Will this work? or do i have wiring wrong for this idea? Also would i need an SPDT or DPDT relay?

PS, all i want is an led to come on when the power goes out.

Thanks, Chris.

Lab Rat

i really dont understand the need for said device unless there is a power interupt switch in series with the relay coil but for you i will explain.
first of all follow the rules of electronics NO DEAD SHORTS ALLOWED
the way you are setting up the relay across the bot power source will create a dead short
you need to put the relay in series with the bots power source not in parallel
the positive from the bots batteries/powersource should be connected to the the common and the normaly open to the bot should be connected to the bot where the source would have connected
next you take your 1.5-3 vdc power supply (you can use 5 volts too as long as you put a 220 ohm resistor in series with the diode) the positive should connected to the common of a different pole of the relay and the normaly closed should be connected to the anode/long lead/or positive of the LED and the cathode/short lead/negative of the LED should be connected to the negative or ground of the 1.5-3 volt dc power supply
now what this will do
when the relay is supplied with the required 12 volts your bot will be turned on and the LED will not be on
when the relay is not supplied with the required 12 volts your bot will will not be turned on and the LED will be on
for future reference the normal state is when there is no power applied the coil

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firealarmfreak

Lab Rat, can you make me a simple diagram for it?

Lab Rat

here you go

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firealarmfreak

Thanks BUT, Lab Rat, Im using the board of education...NOT the boe bot, does that change the diagram or anything?

Lab Rat

sorry my error no it does not just the label that say boe bot

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Mike Green

The BOE in BoeBot stands for Board of Education. That's what's used as a control board for the BoeBot.
You'll need a DPDT 12V coil relay for this.

Lab Rat

it is primarily the same thing
if you are using the 9 volt battery you will need two battery snaps to interupt the power source

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Lab Rat

wow there is too many of us who have nothing to do at the same time

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Lab Rat

oops i forgot to address the relay type part ty mike

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firealarmfreak

LOL I made a good choice to buy a DPDT relay, also Lab Rat, I couldnt help but notice in your diagram there is nothing connected from the - of the boe.. it just shows common going back to + boe.. i dont get that explain?

Mike Green

You only have to interrupt one side of the power supply to cut off the power. Usually this is the (+) lead.

firealarmfreak

i know but how is the boe powered with nothing connected to the -?

firealarmfreak

hey i recreated a diagram to make sure i understood it---is this correct?

Lab Rat

close but the led circuit is not on the same common as the boe
and as for the negative being left alone i was refering to it as the upright connector to the battery that is soldered to the board

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firealarmfreak

oh so do i use one side of the dpdt relay for the boe and the other side for the led, thus the reason i need a dpdt relay instead of spdt?

Lab Rat

here i fixed it


sorry it didnt attatch the file the first try let me try again

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firealarmfreak

where is the fixed attachment?

Lab Rat

sorry it is not working it dont want to attach

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Lab Rat

firealarmfreak said...
oh so do i use one side of the dpdt relay for the boe and the other side for the led, thus the reason i need a dpdt relay instead of spdt?

yea what you said

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Lab Rat

since the website does not want to attach image
to fix your designed image take the +3vdc from the common of the pole it is on and put it on the common of the second pole and take the connection to the nc off of pole one and reaply to the NC of pole two

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Lab Rat

ok i am going to bed no more help from me tonight later

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Chris Savage

firealarmfreak said...(trimmed)
If i were to get a 12 volt dc relay and a 12 volt dc adapater---connect the 12 volt dc adapter to the relay coil---connect the normally closed portion to one side of the boes power, and the common to the other side of the boes power---and then connect an led to the normally open portion, the other side to a seperate 3 vold power source---and the other side of that power source to common (or something like that), would the led turn on when the relay turned off?
What i understand will happen is---when the relay is turned on--the relay will apply power to the boe (board of education), through the normally closed portion. But when the relay loses power and turns off, the relay will turn on the normally open portion, causing the led to turn on.

If you connect the BOE power terminals to COM and N.C. then when the Relay is energized the N.C. terminals will open and the N.O terminals will close.· In your case this would removed power from your BOE.

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Chris Savage
Parallax Engineering

firealarmfreak

I got it working,

thanks for all your help.

Lab Rat

thats good have fun and dont break anything well at least not anything too expensive to replace

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Chris Savage

Okay, now on top of deleting duplicate threads I am tasked with deleting duplicate accounts as well. Posting that your duplicate messages are because you don’t feel like finding your original posts doesn’t make it right. You can your last posts by clicking on your name and seeing the last 5 posts. If that doesn’t work then you can use the enhanced search engine. You’re not going to get help by duplicate posting and creating new accounts. It’s just making more work for me to delete them.· Once again, your duplicate posts have been removed.· I think this makes four times now.

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Chris Savage
Parallax Engineering

firealarmfreak

hey in this diagram i added battery backup. So when the power goes out, the regualar power circuit is open and the battery circuit is closed--alowing my boe and alarms to run off batteries.

then when power is restored, the battery circuit opens and the regualr power closes--alowing my boe and alarms to run on normal power.
im using a dpdt relay.

is this diagram i posted correct? if not can you explain to me why?

chris.