still trying to drive a relay with the Propeller...

gio_rome

Hi,

I'm operating with this:
http://www.abra-electronics.com/products/MR009%252d001.1-Relay-Module.html (+5V relay)

Now, thing is that the above relay _does_ work with the Propeller _without_any_ modifications. Just by plugging in an output pin to the IN relay breakout pin (which has been grounded and powered with +5 VDC). This works even if the Propeller output pin provides +3.3/3.3VDC. (why? don't know...)

This relay breakout is just perfect for me, although not so easy to find (last time I had to wait weeks for the delivery). So I'd want to do without...learn how to do without.

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My constraints are:

+3-3.2V dC to pilot the relay, coming from an output pin from the Propeller chip.
+220 AC, some 5-10A of current / 1000-2000 VA to handle
+monostable relay, so I don't have to check its status....

Why did the above relay work? Was is underdimensioned to work at 5VDC, so that it ended up working even with 3.2VDC? don't know.

I've found something like this (+3V, 10A monostable relay) http://uk.rs-online.com/web/p/non-la...312D3335333326

Sadly it won't be available till november...anyway since I'm here I'd want to check if I understood the wiring...

I connect 6 to propeller out pin, 1 to GND. 3 and 4 are COM and NO...

Can you tell me if I understood right? Also the price seems so low...50 pieces is like 3£ or 4€....
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The initial question stays: what kind of part can I use for my purpose (switch ac mains currents, drive with the Propeller)?

It has also come to my attention (suggested by groggory in another thread like this) this Solid State Relay:

http://www.dx.com/p/ssr-25da-25a-sol...y-white-134494

While it is affordable, seems easy to use, and perfect for the job (or is it?), it's...a little big.
I want to check more if there are alternatives.

Are there any? Suggestions?

tnx in advance for all the support, I owe you big time :-)

G.

T Chap

Not sure what you are saying. You say it works in the first part, then you say it doesn't work. You think the 3.2V is too low? Then get an optofet of some type, connect it to the Prop pin. Put 5V on the other side of the Opto and let 5V trigger the relay. Another option is to apply 5V direct to the relay TTL in, then use a 3904 transistor on the GND side of the relay driven by the prop.

ChrisGadd

You'll still need some sort of transistor driver even with that +3V, 10A monostable relay. They tell you the coil power, resistance, and voltage - 200mw, 45ohm, 3Vdc - which works out to 67mA. The max allowable current for an I/O pin, according to the Prop datasheet, is 40mA. As mentioned in the other thread, the relay module is overkill, all you really need is something like this:

.

gio_rome

T Chap,
I say it works, but I don't know why.
I say I want to do without it, and therefore figure out a way to handle another kind of relay, a +5V relay (+3V relays switch too low currents). Then you suggest to use a transistor to switch the +5V driving the relay / its ground.

Rigth?

G.

gio_rome

ChrisGadd,

thank you for pointing out the lack of current issue. I hadn't thinked about that.

I see your schematics and I recognized it, although I don't understand very well the reason for that "vertical" grounded resistor between the other one and the Base.

Also I had thinked about this configuration already and came out with values like 390 Ohm for the "horizontal" resistor and 2N2222 for the transistor and 1N4002 for the diode (I checked other similar schematics on the web). Would you agree on that?

(also, not to stress the propeller, I use the relay in commond-normally closed configuration)

thank you

g.

Cluso99

For a 5v relay, almost any general purpose npn transistor will work. Any series resistor from 100R to 1K will be fine, and the base-emitter pulldown of 10K to 47K is fine. Transistors such as 2N2222A or P2N2222A (careful, they have different pinouts) or 2N3904/2N3906 (forget which one is the npn) etc are also fine. Diodes such as 1N4001 thru 1N4004 are fine (1A 100V thru 400V) - basically no price difference so 1N4004 hasbecome readily available these days.

The SSR style relays are great because they are optically isolated and you can drive them direct - cannot recall if a series resistor is required - you arejust driving a led.

jmg

gio_rome wrote: »

I'm operating with this:
http://www.abra-electronics.com/products/MR009%252d001.1-Relay-Module.html (+5V relay)

Now, thing is that the above relay _does_ work with the Propeller _without_any_ modifications. Just by plugging in an output pin to the IN relay breakout pin (which has been grounded and powered with +5 VDC). This works even if the Propeller output pin provides +3.3/3.3VDC. (why? don't know...)

The board powers from 5V, which you have done, but it does not need 5.00V @ the IN pin before it turns on.
There is some logic threshold, (volts in and current in) where the relay will close, and another threshold where it will release.
Connect a variable voltage supply to the IN pin, (with 5V to power) and you can measure those two thresholds.
(they will be < 3.3V)

If you read the part values, you can also estimate those values.

StefanL38

Hi Gio,

with some search on youtube I found this tutorial https://www.youtube.com/watch?v=8DMZSxS-xVc
After watching the first 5 minutes I got the impression that the explanations are easy to u nderstand even for beginners

best regards
Stefan