I like it... done a lot with 555 chips... but couldn't design a 555 circuit to do this now... sniff

 

Get a version that can work on your low voltage (and look for through-hole DIP package that you can solder.

 

Where in the world are you? A small 3.3v Arduino microcontroller might be easier to avoid any resistors/capacitors and 3.3v.

 

WOW! it does look like you've done this before. I take it OUT goes to point "A" Frequency could be slower, perhaps a wider pulse width? .. the button no longer exists... only the 555 circuit is in the battery compartment, and external 3 to 4.5 VDC comes in unseen...

 

OK.. to tell the whole story .. the sub will be submerged in mineral oil, in a Micro Ocean..a small display tank that makes waves and shows how they inundate on various shore models.. it's only for educational purposes. I don't build them any more, I just consult to museums and schools who want to have them built. for an example see:

I would like to show the Nautilus near the bottom, where neither waves nor the boat is affected by each other.

 

Use silicone oil because mineral oil will swell into the plastic and cause the plastic to get thick and crack. Use some of your scraps to test. Even test silicone oil.

 

Ou can change the cap to get much slower. I didn't tune the frequency. 10x to 100x cap will give longer pulses and higher value resistor (bottom resistor) will increase pulse duration.

 

Interesting... I had thought of silicon oil... has to be a viscosity close to that of water.. The tank isn't plastic, but the sub is.. all the land models are PVC, Acrylic, and Epoxie .. no issues with mineral oil observed yet. I generally understood the mineral oil to be inert.. will not interact with anything ... it's used to submerge computer components for cooling. and a food safe lubricant.

 

Ou can change the cap to get much slower. I didn't tune the frequency. 10x to 100x cap will give longer pulses and a higher value resistor (bottom resistor) will increase pulse duration.

Thank you...I have some 555's and will breadboard it soon... will let you know what happens.. Thanks much, Regards, Michael

 

Thank you...I have some 555's and will breadboard it soon... will let you know what happens.. Thanks much, Regards, Michael

MrSalts... your input is much appreciated.. I'm a little worried about connecting the output of the 555 chip to Point "A"

This is how I see what we know at this time:

The 555 chip will be applying 3-4.5 VDC to Point "A" (normally at 2.6 to 2.2 depending on if lights are off or on) many times a second... while "A" can go to ground at any time while lights are on.. can it go positive while lights are on? (above 2.2 V)?
Regards, Michael

 

MrSalts... your input is much appreciated.. I'm a little worried about connecting the output of the 555 chip to Point "A"

This is how I see what we know at this time:
View attachment 245610
The 555 chip will be applying 3-4.5 VDC to Point "A" (normally at 2.6 to 2.2 depending on if lights are off or on) many times a second... while "A" can go to ground at any time while lights are on.. can it go positive while lights are on? (above 2.2 V)?
Regards, Michael

Most likely, the Point A is the input to a logic chip or a microcontroller or (most likely) the trigger (pin 2) of a 555 timer. These are high input impedence and no significant current will flow out of point A to ground.

Let's try, connect your Nautilus to your breadboard power supply. Touch a 1k Resistor across Point A and Point B to see if it triggers. If not, try a 100 ohm.

Also, measure voltage across Point A and Point B when you are powering the Nautilus from your breadboard.

 

EDIT - I didn't see your image (didn't load. I have some slow wifi issues). Ok,

If you put a 100 to 1000 ohm resistor between Point A and your 555 output, we should be quite safe.

 

And here is some better cap and resistor sizes. For 2 pulses every 3 seconds. 0.629 Hz (629milliHz in oScope chart below).

 

This is the safest method (assuming you have a small NPN transistor (2N3904, 2N2222a or BC337, or anything you find).

This way, the voltage at Point A will be connected to ground when the 555 goes high. This way, no higher voltage is applied to the Point A.

 

You are awesome MrSalts .. I will make it happen.. if it works.. you get a bag-o-Lindt-chocolate truffles PS: I think I have all the parts &
0.629 Hz ought to be fine ...

 

You are awesome MrSalts .. I will make it happen.. if it works.. you get a bag-o-Lindt-chocolate truffles PS: I think I have all the parts &
0.629 Hz ought to be fine ...

My biggest concern is what the mineral oil will do to your plastic. Injection-moldable plastics are much more susceptible to swelling than cast resins that polymerize in the mold. Please check if your scraps from the cut-off bottom will be compatible with your mineral oil.

 

Hmmmm... I'll let you know how that goes...it is going in the mineral oil

 

Most likely, the Point A is the input to a logic chip or a microcontroller or (most likely) the trigger (pin 2) of a 555 timer. These are high input impedence and no significant current will flow out of point A to ground.

Let's try, connect your Nautilus to your breadboard power supply. Touch a 1k Resistor across Point A and Point B to see if it triggers. If not, try a 100 ohm.

Also, measure voltage across Point A and Point B when you are powering the Nautilus from your breadboard.

I did measure the voltage from A to B (that yellow paper where I show what we have. Post. # 30

 

EDIT - I didn't see your image (didn't load. I have some slow wifi issues). Ok,

If you put a 100 to 1000 ohm resistor between Point A and your 555 output, we should be quite safe.

I'll try that when I get home... Looks like you are thinking about not using the NPN switch?

 

You also might be able to pull it off with an LT6700 It comes in 3 different varietes. https://www.analog.com/media/en/technical-documentation/data-sheets/6700123fh.pdf One does both polarities. There is also a one comparitor version of the chip.

You need a resistor to drop some voltage. Lets use 400 mV. So, you need to say if it;s less than 400 mV turn it on. Turning it on will make it >400 mV, so it turns off. There might be a problem as to how long you have to press the button.
So, you would put some resistor that drops >400mV in series with the power negative. or maybe power positive,. Look at the datasheet.
400 mV is the minimum you can set using this part.

You MIGHT need to extend the pulse,