Now Available: Momentary Switch for Red-dot-finders

[Garbz]

Following on from this thread: http://www.iceinspace.com.au/forum/showthread.php?t=116296 I've made a small circuit that will provide temporary power to a red-dot-finder to reduce the number of batteries I go through. Push the button and the red-dot-finder will power up for 60 seconds and then turn off again. I built the system into my finder and because of interest I had a few circuit boards made up which are now on offer.

I have the following choices to give out as per the picture below:

1. A powered version. This takes a coin cell and when pushing the button provides power to the red dot finder. It can be installed into red-dot finders without modification (hopefully) by attaching the red and brown leads to the +ve and -ve terminals of the battery holder in the finder.

2. A small non-powered version which needs to be installed in-line in the electronics inside the red-dot finder. The orange and yellow cables will attach to the existing battery holder and the green / blue cables will attach to one side of the laser diode and the other side of the existing current limiting resistor / potentiometer.

I'll post pictures and instructions tonight.

3. A third option for those willing I'll post unpopulated boards and components if anyone wants to try their hand at some surface mount soldering, or alternatively the powered version can be made with normal through hole footprints on components controlling the timing allowing you to customise the how long the circuit stays on for by tweaking the values of (C1 and R1).


$10 for any of the above varieties + postage. Or no postage if you want to pick it up in Brisbane.

I believe I have 3 of the powered versions, and 8 of the non-powered versions remaining. Probably more if the people who were previously interested are no longer.

[GraemeT]

PM sent.

[Garbz]

Sorry all I've been rather ill for the past week and have not had the mental capacity to work on this. Fortunately things are looking up now and I'll head to the post office tomorrow to enquire about shipping.

In the mean time I've jotted down some installation instructions. A bit of electrical splicing will be needed to get the small version working, however the larger version should be quite easy to install if you can figure out how to connect it to the battery terminals.

A typical circuit inside a red-dot finder will have a battery, a switching / brightness mechanism, and the laser maybe including some current limiting resistor along the way all hooked up in series.

Installation for the small version:

Open the Red dot finder and identify the cables that go from the battery to the rest of the circuit.
Cut the batteries from the rest of the circuit.
Connect the Batt+/- terminals of the momentary pushbutton to the battery.
Connect the Dot +/- terminals of the switch to the rest of the circuit. Effecively you've just spliced this thing in the way of the battery.
Turn on the red-dot finder and then press the button and it should light for 60s.


Installation for the large version:

Remove battery from red-dot finder.
Connect the +ve and -ve terminals to the + and - leads of the battery holder *
Turn on the red-dot finder and then press the button and it should light for 60s.

* The idea is to replace the battery with this circuit. To connect to a typical coin cell battery you need some way of pressing the leads to either terminal in the battery holder. A small 20mm circle of bulsa wood, or a small disc of plastic would do the job. I have had success making a sandwich of a 5c piece, the wire, a folded piece of paper, the other wire, and another 5c piece and slot that mess into where the battery goes (see picture). Though I'm sure some of you clever people could think of something more reliable, such as the same thing with a lot of hot glue :D

** Erratum on attached picture instructions: The picture shows the potentiometer attached to the high side of the laser and cables setup such that green > potentiometer, and blue > laser. Based on feedback some finders may have the potentiometer installed on the wrong side of the laser. In this case swap the green and blue leads in the instruction so that green > laser and blue > potentiometer.

You can't damage your red dot finder if you plug in this unit backwards. Laser diodes act like LEDs and will only pass current one way so hooking it up backwards means you will simply see no signs of life.

[Garbz]

Ok shipping works out to be approximately $4 to cover postage and padded bag. Can easily get multiple units in a bag. Just need to check if the large unit will fit in too, if it hits the parcel limit it'll be $7.

I have 3x big and 8x small versions not yet assigned to someone.

[allan gould]

Can you PM me?

[rcheshire]

Thanks Chris. Arrived safe and sound.

[Garbz]

Yes but does it work ;)

1 big powered unit and 8 small unpowered units left (I found another set of 5 in the bottom of the box). Beyond that there will be a backorder.

[Garbz]

Just an update for anyone thinking of buying the last powered unit, it's $8 for postage. Post office wouldn't let me post it as a letter.

Unless of course you have a soldering iron and are comfortable in soldering in the switch yourself, in which case I'll leave that component off the board and you save yourself $4.

1 big powered unit and 7 small unpowered units left.