First off I just want to say I'm a total newbie...
I'm trying to get the electronic figured out before I start to program.
Im using an optical liquid sensor to activate a DC water pump when the water level becomes low in my fish tank. I've got most if it figured out except for one problem I'm having. When the sensor triggers the sainsmart SSR it turn ON the pump the SSR does not turn off the 9v DC pump, it just stays on.
What am I doing wrong?
**edit is for changing 12v to 9v
I believe a SSR is essentially a triac. This is from a Wikipedia page: "Once triggered, the device continues to conduct until the current drops below a certain threshold called the holding current." - Scotty
Model number of your SSR would help greatly in understanding what you are attempting. What is the purpose of the relay board.
If it's a simple DC pump you are controlling then a FET would probably be a better, and cheaper, choice.
Plus, that's not a circuit - it's a collection of inter-connected components. A circuit diagram should graphically (ie drawn) show how each component is electrically connected to others. Proprietary devices, such as the arduino, can be shown as simple boxes, with i/o, power and control points clearly identified
Then we may be able to assist.
Please draw a schematic with pen and paper of how it is wired and take a photo with your cell phone and post it.
Assuming the SSR is controlled by an arduino
AND IS WIRED CORRECTLY , there is no reason it should not turn off. When it is ON, try placing a 1k resistor across the INPUT terminals (the one connected to the arduino) . If it does not turn off then , there is definitely something wrong.
Im using the relay board to turn on a pump when the optical water sensor triggers it. At the moment have the sensor wired directly into the relay board but eventually I program an Arduino to trigger he on/off of the pump based on the status of the optical water sensor.
This is the relay board Im using.
raschemmel:
Please draw a schematic with pen and paper of how it is wired and take a photo with your cell phone and post it.
Assuming the SSR is controlled by an arduino
Solid State Relay Guide - Phidgets SupportAND IS WIRED CORRECTLY , there is no reason it should not turn off. When it is ON, try placing a 1k resistor across the INPUT terminals (the one connected to the arduino) . If it does not turn off then , there is definitely something wrong.
Here is a schematic drawing of my wiring, sorry if its not that clear,this is all new to me.
ATO.pdf (435 KB)
FORGET THE SENSOR ! The question we need to answer is will the pump turn on AND OFF if you simply connect +5 to +24V dc
to the dc input pins of the SSR. Until you have done that test , everything else is irrelevant. When you post the results of that
test then we can address any sensor related issues. ok ?
Sorry to have to tell you this but you can't use an SSR designed for switching AC devices to switch a dc pump motor.
Look at the specs for Output
raschemmel:
FORGET THE SENSOR ! The question we need to answer is will the pump turn on AND OFF if you simply connect +5 to +24V dc
to the dc input pins of the SSR. Until you have done that test , everything else is irrelevant. When you post the results of that
test then we can address any sensor related issues. ok ?
agreed, i don't think he sensor is he problem. I did try to wire the pump and SSR to without the sensor and I was still having the same problem of the pump turning on when the SSR is triggered but remains ON then after the trigger is removed. The SSR LED indicator turns off when the trigger taken off but the pump still remains ON.
If the relays are not rated to switch DC, they will likely not work. Most devices that switch AC use Triacs or SCR's (two SCRs are similar to one Triac), which work in the same way. They turn on and latch on until the current goes to zero. With AC that happens with the next zero crossing (100 to 120 times a second depending on your AC line frequency (50 or 60 hz)). With DC they will go on and latch on until something else turns the current off.
With regular mechanical relays the DC rating is usually lower than the AC rating. That is for a similar reason. When the contact opens an arc will start. With AC the arc will tend to extinguish at the next zero crossing. With DC the arc will continue until the contacts are far enough apart to extinguish the arc. Once an arc starts it tends to continue because the air is ionized which gives it a relativly low resistance.
http://bbs.homeshopmachinist.net/threads/50917-Solid-state-relay-question
raschemmel:
Sorry to have to tell you this but you can't use an SSR designed for switching AC devices to switch a dc pump motor.
OMRON 2/4/8-Ch 5V Solid State Relay | SainSmart – SainSmart.comLook at the specs for Output
good find! Thanks raschemmel, don't know how I missed that.
Are there any alternatives for my SSR that you would suggest that could swich DC motors?
Can SSR's even switch DC motors?
Simple dc relay .
What is the rated current for the pump motor ?
Are you in the USA ?
raschemmel:
Simple dc relay .
What is the rated current for the pump motor ?
Are you in the USA ?
9v at 1000ma
Yes im in the US
You need a 2n3904 or 2n2222 transistor and one of these
a 1k resistor and you'll be in business.
raschemmel:
http://www.radioshack.com/product/index.jsp?productId=2049716You need a 2n3904 or 2n2222 transistor and one of these
Schottky Diode - COM-10926 - SparkFun Electronics
a 1k resistor and you'll be in business.
Thanks for all your help.
I didn't get a chance to see you message before I went to radio shack this afternoon, so I ended up using a TIP120 Darlington transistor. It seems to be working just fine. you think this is a good option or should I do the relay?
That's fine. Do you have a diode on there ?
Yes, I used a 200v 1a diode.
Great. Glad you got it working.
