RF receiving and Power saving too?

[212]

Working on my little video camera project still, and I am using some cheap 315mhz RF units for remote triggering, to turn it on. Thanks to the good doc's code, I have it working OK, but I sure would like to save some battery power too...

My little receiver has to be on all the time, I know that, and it uses about 200ua. My question for you is...can I save any power being used by my 08M??? I tried a few things already, but I have not had success saving power and have it still work lol...

Here is the receiver code, I borrowed most of it


low 0
low 1
low 2

disablebod

main:

serin 4,N2400,("TW"),b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13
b13=255-b13' inverse again only need to really test one
if b12=b13 then

high 2
pause 10
low 2
endif
goto main

 

[lbenson]

Since you are basically sitting in serin all of the time, I'm not sure how much battery power you can save, but is there a reason you are reading in b0 through b13? The doc was showing how you could send that many variables if you needed them. If all your code does is snap the picture, you don't need anything more than

serin 4,N2400,("TW")

Having gotten past the serin by receiving "TW" (or any other receiver-specific qualifier) tells you all that you need to know to go ahead and snap the picture. Of course, if you are using the other variables to perform other functions, just ignore this post.

With "disablebod" your picaxe will probably continue to operate at a far lower battery voltage than your 315mHz receiver will. You might want to put a transmitter on this module, and monitor the battery voltage with ADC and send it back every once in a while.

 

[moxhamj]

200uA while waiting on a serin is pretty good! You could put it into sleep mode for a minute and wake up for 5 secs and only send signals every minute, but you need to synchronise things. Rechargeable batteries will last a long time at 200uA. Or you could use a solar panel - it wouln't have to catch much sun. How far away from mains power is the unit?

 

[212]

lbenson, I really have no idea what I'm doing yet, I barely can copy stuff. I'll make the changes...thanks

Originally I was going to use an encoder and decoder chip, but had issues fitting it inside the camera's case with all the rest of the stuff I need. I have a commercial "camera controller" in there too, to do the actual camera timings for me. I tried to use "count" to read what was being sent, but did no good with that??? So I put a picaxe to use on both ends and used the code from Dr_Acula's how too.

Doc, I did not mean to mislead you, the receiver alone uses about 200ua, then the picaxe is added. I been trying different things and forgot exactly, but I believe the total is around 500ua~600ua with a 3.6V regulator running it....maybe 800ua straight off the batteries.

I need quick response time, so I have to have the thing ready to go at any moment. The unit will be out in the woods watching wildlife, so I'd need a long long wire to use mains power. I tried slowing down the Picaxe, but then it quit working. I can put it to sleep, but not for long at a time, so I saw little gain...or loss I suppose...with that. It's just a toy, and I can live with it the way it is now, I just wanted to know if there might be a trick or two I missed.

It will need to be painted a pretty "camo" pattern, and I'll neaten it up inside too, but here is what it looks like so far. The camera is a Jazz DV150, and is IR modified. In separate cases are the remote sensors, and in them too, I have IR illumination for it. Usually the PIR would be looking out the case with the camera, but having a remote sensor allows me to make it smaller and hide it better....well once I get it fixed it will

 

[Dippy]

The usual way to save power using RF receiver modules is to 'Duty Cycle' them. The downside is slower response. Examples using this method include Radio Doorbells.

Basically, you briefly power-up the module (say 100mS), if a signal appears keep it switched on until signal disappears, or if no signal switch off for 500mS. But, it does mean the transmission has to be longer than the off-time. Fine for doorbells...

This can be done with a 555 circuit or with a PICAXE using the ADC circuit. On many modules you can use the Data pin to trigger the monostable (software or hardware), but the best method is to trigger it using the RSSI output. Sadly, not all 'el cheapo' modules have this pin.

 

[moxhamj]

If you want it to last forever then maybe solar but I suspect the hassle isn't worth it. Say it draws 1mA. That is 24mAH per day, 240mAH per 10 days, 2400mAH per 100 days which is probably the capacity of alkaline batteries. Is 100 days too short? Or you could go rechargeable - there are lots of 2400mAH rechargeables around now.

 

[212]

Nope, these receivers do not have any RSSI output, but that's OK, they are fine for what I will use them for. I did duty cycle the picaxe on the transmitter side...well I slowed it down and put it to sleep for a time, and it uses practically nothing. Funny thing is, the light uses about 1.4 amps when it is on, so that was silly huh...

I think I will play with turning the receiver on and off, I thought it needed to be for seconds instead of only fractions of seconds. Learning all the time...thanks! I'm not necessarily needing to do anything more, I'm just trying to learn how to use the chips to their best ability is all. If I was really concerned about saving every drop of power I would go back to the PT2272...it uses only 0.1ua on stand-by!!!

Dr_Acula, I'm in South Texas, and you and I both get enough sun to power just about anything we want huh. No, I don't really need the little thing to go on forever, the memory will only hold about 2 hours of video anyway, I'm just having a good time

Thanks for the help guys!

 

[Hooter]

If you are looking for a Transceiver with an RSSI output check out the Hope-RF RF12 and RF12B at around $US 8 each.
Hooter

 

[212]

I've been reading all the posts, but I'm thinking those are beyond my...skill level? I'm hoping some other dumb guy, like me, will get some and have you guys help with setting them up. That way I don't have to ask and look like the dummy

 

[212]

OK...ummm...I have changed the transmitter to this"

main:

if pin3 = 1 then
serout 1,N2400,("TW")
pause 1000
endif
goto main

And I can change the receiver to this easy enough too:

serin 4,N2400,("TW") But I am lost past there. Where would my if...then be? Or will it just go down to the next line only when it hears TW???

 

[lbenson]

212--right--you don't need the "if" statement. Your receiver will be in "serin hang" (meaning no other statements will be executed past the serin) until "TW" is received. When it is, you can immediately click your shutter and go back and listen for the next "TW". Usually "serin hang" is a bad thing, but if you don't want to do anything until you receive a transmission, it works for you in this case.

 

[212]

Roger that, thanks!