Trouble with my automatic door circuit

Thread Starter

craxe77

Joined Jun 9, 2016
11
Hey all,
Having a bit of trouble with my automatic chicken door circuit. I set everything up as seen in the below picture and when testing I smoked both relays and the door up switch. Not sure what I did wrong. Is my battery amperage to high? The battery is a 12v 4Ah battery. Relays are 12vdc rated and I thought good to 10amps. The only thing I did extra from the schematic is add an additional connection from the positive battery terminal to one side of both relay coils and the negative side of the relay coils I tied and extra line to the door switches. I have not attached the solar panel yet.

Any Ideas?upload_2016-6-9_8-23-1.png
 

Dodgydave

Joined Jun 22, 2012
11,342
Dont see the point of the relays,,,, looks to me the relays are wired wrong,, they should be changing the polarity of the motor.
 

MaxHeadRoom

Joined Jul 18, 2013
28,820
You battery capacity will not affect the current draw, the demand will be whatever the load requires.
Do you have part no's on the timer & relays?
It looks like it should work unless you have changed the circuit as mentioned
Max.
 

Thread Starter

craxe77

Joined Jun 9, 2016
11
Maybe the solenoids set up wrong like you said. Your right that the motor would not run backwards in the current setup. I redrew the circuit below. Still not sure why I smoked the relays and a SPST door upper limit switch.

Here are the part numbers. I bought them from sears.
-Timer is model# a12031200ux0076 Link is http://www.sears.com/unique-bargain...mable/p-SPM7783774423?redirectType=SKIP_LEVEL

-Relay is Model # a13122300ux0029 . Link is http://www.sears.com/unique-bargain...netic/p-SPM7969143623?redirectType=SKIP_LEVEL

My battery is:
upload_2016-6-9_10-6-53.jpeg

Maybe if I set up circuit as such?
upload_2016-6-9_10-8-25.png
 

Thread Starter

craxe77

Joined Jun 9, 2016
11
OK I see what you mean and I went back and looked at my circuit. I shorted out the voltage by following that second drawing. Would this have smoked my relays? As soon as the timer switched and energized the relays everything started smoking in that circuit.
 

SgtWookie

Joined Jul 17, 2007
22,230
You just need two SPDT relays, one for each motor lead. You can use your DPDT relays, but just use one contact set in each relay. Wire a motor lead to the common terminal, the NC (normally closed) terminal to bat -, the NO (normally open) terminal to bat +. That way there are no possible combinations that would result in a shorted battery. SPDT automotive relays work fine for things like this.
 

crutschow

Joined Mar 14, 2008
34,827
You need to connect it so timer switch and limit switches go to the relay coils only, with the relay outputs controlling the motor, using the connections shown in Dodgydave's reference.
You don't want the motor current going through the switches.

Also you should add transient protection diodes to prevent the motor inductive spikes from arcing across the relay contacts and damaging them.
You need 4 diodes as shown below:

upload_2016-6-9_9-4-9.png
 

Thread Starter

craxe77

Joined Jun 9, 2016
11
You need to connect it so timer switch and limit switches go to the relay coils only, with the relay outputs controlling the motor, using the connections shown in Dodgydave's reference.
You don't want the motor current going through the switches.

Also you should add transient protection diodes to prevent the motor inductive spikes from arcing across the relay contacts and damaging them.
You need 4 diodes as shown below:

View attachment 107468
Thanks for the help so far. Definitely interested in protecting the relays but I'm a noob when it comes to electronics and schematics so let me see if I have this right. I should put the transient protection diodes on the 4 wires coming off of my motor +/- on one contact and -/+ on the other? Also, should they be bi-directional?
 

Thread Starter

craxe77

Joined Jun 9, 2016
11
Update- everything is up and running well. If I had correctly followed the original plans then all would have been good right off the bat. Dodgydave pointed out that I would short out my voltage if I followed my second drawing which made me go back and take a good look and see that yes I did wire incorrectly.

I also am ordering 4 transient protection diodes to protect my relays. Thanks again.
 

crutschow

Joined Mar 14, 2008
34,827
Thanks for the help so far. Definitely interested in protecting the relays but I'm a noob when it comes to electronics and schematics so let me see if I have this right. I should put the transient protection diodes on the 4 wires coming off of my motor +/- on one contact and -/+ on the other? Also, should they be bi-directional?
What do you mean "bi-directional"? :confused:
The diodes, as shown, will protect for the motor going in either direction (either motor terminal positive with respect to the other).

The (+) on the motor is just to show the forward direction of the motor for that polarity of applied voltage.
 

Thread Starter

craxe77

Joined Jun 9, 2016
11
What do you mean "bi-directional"? :confused:
The diodes, as shown, will protect for the motor going in either direction (either motor terminal positive with respect to the other).

The (+) on the motor is just to show the forward direction of the motor for that polarity of applied voltage.
I was not familiar with these types of diodes so I researched them. They are sold as either both unidirectional or bidirectional.

I figured out after I posted that unidirectional was whay I should be doing.
 

Dodgydave

Joined Jun 22, 2012
11,342
The only bi-directional diode is a Diac, which is used in ac control circuits. The diodes here are for suppression of "back emf spikes" from the motor.
 
The only bi-directional diode is a Diac, which is used in ac control circuits. The diodes here are for suppression of "back emf spikes" from the motor.
NOT TRUE.

http://www.littelfuse.com/~/media/e.../littelfuse_tvs_diode_1_5ke_datasheet.pdf.pdf

Note the "Bi-directional" version in the "functional diagram".

I could argue that any diode is "bidirectional", BUT I WON'T. An ~0.6 V drop in the FWD direction and a non-destructive clamp at the reverse voltage point.

Aside: I won't argue that paper is conductive, but it is. You can easily measure pA of current with probes on a piece of paper and it changes based on humidity. An Acetone film on a piece of glass is conductive at those levels.
 
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