PIC relays control

[flipper_md]

just a little follow up on this

Finally ,I had to order 4.5V relays cuz order 5V we're not stock.
By time things arrived, I spoke with a few people and one told me that some relays were designed to be driven by IC, without anything special requd for protection.

I then decided to give it a chance, and it work! First without a bi-color LED on the pins of the coil, but this would take to much power and only the led would light up.
Removed the led, relay started switching, and kept going

since then I've being debugging/coding for a while, and no problem to report, for the relay.
Coding is another challenge

relays PN is AGN2104H

[Pic_User]

just a little follow up on this

Finally ,I had to order 4.5V relays cuz order 5V we're not stock.
By time things arrived, I spoke with a few people and one told me that some relays were designed to be driven by IC, without anything special requd for protection.

I then decided to give it a chance, and it work! First without a bi-color LED on the pins of the coil, but this would take to much power and only the led would light up.
Removed the led, relay started switching, and kept going

since then I've being debugging/coding for a while, and no problem to report, for the relay.
Coding is another challenge

relays PN is AGN2104H

Hi Dom,

Glad to hear you are making headway. Thank you for the follow-up information. We are all on the learning curve of life.

It is good to get technical advice from knowledgeable people.
Always double check information, at least till you find out which information sources are reliable.

Always read the data sheet.
Always “do your home work” with the technical briefs.

AGN2104H Relay
4.5V nominal 6.75V maximum

If you look at the AGN2104H data sheet:
http://pewa.panasonic.com/pcsd/produ...pdf_cat/gn.pdf

For Cautions for Use, see “Relay Technical Information”.

That brings us to here:
Relay Technical Information (PDF:400KB)
http://pewa.panasonic.com/pcsd/product/re/rti.pdf

Countermeasures for surge voltage of relay control transistor
If the coil current is suddenly interrupted, a sudden high voltage pulse is developed in the coil. If this voltage exceeds the voltage resistance of the transistor, the transistor will be degraded, and this will lead to damage. It is absolutely necessary to connect a diode in the circuit as a means of preventing damage from the counter EMF.

In the Technical Brief, they are assuming you are driving the relay with a discrete transistor. If you are driving from a PIC then the “transistor” is really inside the PIC. The same precautions apply.

Hope this helps,
-Adam-

[flipper_md]

Thanks much for the check Adam!

I admit I'm a bit lazy at reading tech stuff, and I kinda trust a lot electonic components, just like mechanical parts
I fear only things when they start to smell weird, burn my fingers or don't light up anymore.
Further more, i'm not skilled at welding so less means better!


I understand I might be hurting the poor PIC now, but I'm just so curious to see how long he will take it that I can't get myself to puts some diodes in.
By caution I measured the peak voltage on my fluke(112), it says 3.3V peak after a couples switch, but is that reliable? The FLuke alone may buffer the voltage?

those tiny processor are heck of fun to play with, it's never ending!

... if I had a girlfriend, she d probably wish to be a PIC 8)

[Kalind]

I need to know how to write the code to switch on/off a relay when a temperature setpoint is reached. The output pin im using is RC1 of a 16f873. Please, someone help me!!

[skimask]

I need to know how to write the code to switch on/off a relay when a temperature setpoint is reached. The output pin im using is RC1 of a 16f873. Please, someone help me!!

main:
if temp > setpoint then
     portc.1 = 1
else
     portc.0 = 0
endif
goto main

You write code by typing at the keyboard.

[earltyso]

I have been using the OMRON G3MB-202PL DC5 solid state relay for my AC christmas lights controller. They only pull ~15mA (input impedance is 440ohms +/- 20%) and work great for switching. The voltage input is 4-6V for on. I drive them directly from my pics and have had no problems. I can tell you that it is a GREAT idea to include fuses in your circuit when you use these if you are planning on large loads 1A+. The best part is that the snubber is built right in the SIP package. They go for 4-5.50 from DIGIKEY part #Z915.

From this forum I learned how to hold the state on or off with a simple counter.
I use this to

main:
if button = 0 then
i = i +1
'blah blah
endif
gosub choice
goto main

choice:
if i.0 = 0 then
high relay1
endif
if i.0 = 1 then
low relay1
endif