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I need some assistance
By David HK, Section Rants & Opinion Posted on Thu May 8th, 2008 at 10:42:20 AM MST
Lost on the electronics bit

Can someone help me off board?
I have constructed the hardware for a 'gecko' and 'cockroach' catching machine. Its quite elegant.
The arrangement involves an infrared transmitter diode sending to a photodiode which in turn is picked up by a 2N3906 transistor - the output is high or low - x volts or zero. This is to detect the gecko or cockroach inside the machine.
I have a 12 volt solenoid to pull the pin on the trap door.
To allow the trapdoor to fall freely I need to hold the actuator pin inside the solenoid coil for about 1.5 seconds. I have been playing with a 555 IC to achieve this and studied it so much that I have become lost - all fails.
After the system has 'actuated' and the trapdoor falls, I want to turn off the entire circuit power to conserve the battery. I was thinking of a magnet and reed switch, but there must be something more simpler.
The power supply can be between 9 and 12 volts DC with battery, or, with mains DC by converter, but the solenoid is a bit slower with 9 volts.
I have photos etc, and if you can assist a 60 year old who is of 'fumbling amateur status" I should be very grateful.
At a push I am hoping to use solar power for charging which may be a poor excuse to keep this on the board for a short while.
My diect e-mail is strltd AT netvigator.com Change the obvious.
David HK

I need some assistance | 12 comments (12 topical, 0 editorial)

Re: I need some assistance (3.00 / 0) (#1)
by DamonHD (d@hd.org) on Thu May 8th, 2008 at 04:52:31 AM MST
(User Info) http://www.earth.org.uk/

What about powering the whole thing via a small relay or power FET that need power to stay on, and when the power is cut it needs a manual reconnection to the power to come on again, bootstrap style?

When the trap has dropped the circuit pulls its own plug as it were, and needs you to reactivate it (and squish the roach) manually.

Rgds

Damon

Re: I need some assistance (3.00 / 0) (#2)
by David HK on Thu May 8th, 2008 at 05:12:17 AM MST
(User Info)

Damon,

I've thought about that, but relays require power. Also, after the trap has tripped, the reptile inside may move around and keep retriggering the circuit all to no avail, hence the need for the entire circuit to be turned off.

David

[ Parent ]

Re: I need some assistance (3.00 / 0) (#5)
by DamonHD (d@hd.org) on Thu May 8th, 2008 at 05:40:52 AM MST
(User Info) http://www.earth.org.uk/

But the power to the relay coil can come through normally-open contacts in parallel with the rest of the circuit.

Once the contacts get opened no more power drawn by the coil or the rest of the circuit.

It depends on the duty-cycle, ie what fraction of the time you expect the circuit to be armed and waiting vs brooding with a bug in its bowels.

Rgds

Damon

[ Parent ]

Re: I need some assistance (3.00 / 0) (#6)
by David HK on Thu May 8th, 2008 at 06:25:31 AM MST
(User Info)

Damon,

The system needs to be active from the time the last person in the household goes to bed - say midnight - until about 5am when I get up every morning in the summer time, or, 5.30 am when I get up in the winter.

On time is around 5 hours so there must be a circuit that can cope with this and consume minimum battery power.

Cockroaches are normally given the size 8 shoe, but geckos are useful creatures and eat ants and mosqitos etc. I never kill these amazing little reptiles and only want to catch them and then transport them several streets away so they can live somewhere else. Catching insects is not a problem with geckos; its their crap that they leave on their 'runs' which I consider a hygiene problem, hence my desire to catch and release them.

David HK

[ Parent ]

Re: I need some assistance (3.00 / 0) (#7)
by DamonHD (d@hd.org) on Thu May 8th, 2008 at 07:15:04 AM MST
(User Info) http://www.earth.org.uk/

Hi,

Well, some relays use very little power, but consider a power FET which need take practically no power at all (down to nanoamps) to be held 'on' depending how you do it.

Or have the logic run on CMOS (4xxx series, good from ~3V to 18V) with a latched output to disable the power to the rest of the circuit, manually resettable. Look at something like the 4007 + pull-up resistor + P-channel power MOSFET to gate power to the rest of your system.

Microamps should cover that when inactive.

Rgds

Damon

[ Parent ]

Re: I need some assistance (3.00 / 0) (#12)
by ZooT on Wed May 14th, 2008 at 02:14:50 AM MST
(User Info)

A microswitch setup in normally open and activated or closed by the open door would shut the circuit down when the door dropped and deactivated or opened the switch.....
As far as that goes though.....a couple little strips of copper could do the very same thing and could probably handle a higher current too

[ Parent ]

Re: I need some assistance (3.00 / 0) (#3)
by briskwinds on Thu May 8th, 2008 at 05:21:40 AM MST
(User Info)

Attach a capacitor parallel to the solenoid so that it can power the solenoid for 1.5 seconds.(Trial and error method to find the time delay you want).

Re: I need some assistance (3.00 / 0) (#4)
by Basil (basil(spamblock)key@bellsouth.net) on Thu May 8th, 2008 at 05:24:23 AM MST
(User Info)

I like your idea. Good luck and wish I could help. I would have to just us a rolled up news paper for my cockroach's.
Bad luck or none at all.

Re: I need some assistance (3.00 / 0) (#8)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Thu May 8th, 2008 at 09:29:50 AM MST
(User Info) http://wooferhound.com

Opto SCRs might work in this situation, kinda like a relay that only pulls enough power for an LED.

-quote-
"At a push I am hoping to use solar power for charging which may be a poor excuse to keep this on the board for a short while"

I would like to see an area on the forum called "Shop Talk" for discussions about our other projects that aren't related to Renewable Energy . . . like this one.
W o o f -={(

Re: I need some assistance (3.00 / 0) (#9)
by commanda (alwynne at unwired dot com dot au) on Thu May 8th, 2008 at 03:09:44 PM MST
(User Info)

Use a 4093, quad nand with schmitt trigger inputs. And a fet for the power switch. The 4093 can be left on continuously; it's cmos and draws very little current.

2 gates are wired as a flip flop. Push button switch to one input to activate it. Photo sensor fires solenoid and drops gate. Signal from photo sensor goes through one 4093 gate with a 1.5 sec RC constant to the reset input of flip-flop which then turns the power fet off.

Flip-flop inputs are normally high and switch to ground.

Contact me directly if you need further help.

Amanda

Re: I need some assistance (3.00 / 0) (#10)
by David HK on Thu May 8th, 2008 at 03:47:57 PM MST
(User Info)

Ladies and Gentlemen,

Thank you all very much for your encouragement.

Amanda, I shall indeed give your excellent suggestion a days work and let you know the outcome. I am not that bad at following electronic circuits, but sometimes ones mind can get very wrapped up to the point of understanding confusion.

I shall report back later.

David HK

[ Parent ]

Re: I need some assistance (3.00 / 0) (#11)
by commanda (alwynne at unwired dot com dot au) on Thu May 8th, 2008 at 04:35:15 PM MST
(User Info)

http://www.otherpower.com/images/scimages/2006/0213_001.pdf

I need some assistance | 12 comments (12 topical, 0 editorial)

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