This is not an arduino question. It is about an addition to my highly arduino-controlled hen house, but it is an attempt to do things analog.
So, side question: where is the best place to go other than this forum for the kinds of electronics project advice below?
On the the main quesiton. The problem: A fox recently killed 16 chickens. First attack in 8 years. There are a lot of foxes around, so hopefully the long interval before any troubles suggests our other anti-fox measures are not too bad. But before we re-stock, I'd like to do a few upgrades.
I had thought it was a gimmick, but I now have it on good authority that devices that light up two red LEDs like evil predator eyes, such as
are actually effective.
I'd much rather do this myself! Also, I feel that if they blink once a minute or so, it might make them a bit harder for a fox to habituate to. I've set myself a challenge to make these myself with the most basic components I can. I already have 5V in the chicken house because there is a fair bit of automation going on already.
Here is a schematic of my prototype (only development so far is building it on a breadboard this afternoon). The basic idea is to use a phototransistor to make a light-dependent switch. When the system comes on (low light), a highly asymmetric astable multivibrator circuit controls the LEDs such that they are on for about 50s between 1s blinks.
I would welcome any feedback. My analog skills are weak! Basically I used 2n2222 for everything because I have a bag of them. I wouldn't know better if there were obvious better choices for any specific parts of the circuit. Also, I'm having to do a darlington pair system to amplify the output of my the light sensing circuit, at least when its sensitivity is tuned to dusk/dawn. Could someone suggest a better way (maybe someone has used a different phototransistor that is better for this kind of situation)?
I agree with the Arduino suggestion. You could then also add fading effects for greater realism.
If you continue with the existing circuit, I think you have to invert the electrolytic capacitor.
Totally get you. The hen door, various monitoring and reporting by packet radio, etc are already all a low power ATmega328p-based scheme. I may end up going that way for the this part of the system too (pulsating glowing eyes!). But part of my goal here is also to try to get a bit more competent on the analog side of things!
Hi Larry - indeed I started with that, then challenged myself to go to even more basic components. What would you see as the benefit? I didn't get to testing the contribution of the current consumed by the 555 to the circuit as a whole. The multivibrator part as currently set up seems to contribute a consumption of about <1mA, so I'm not sure if it would pay off current-wise to go back to a 555.
I occasionally get my circuit failing to start up when I cut the light. I can't quite decide if it is the general unreliableness of the breadboard, or if there could be something unreliable about the design.
Indeed! Yes, you are right it is supposed to be the other way. I'm a bit confused at why it seems to work either way around! Trying to puzzle through the logic of why it would work either way around in my case, but can't piece it together.
