Project: Bat Detector

 

Summer is almost upon us and with it comes the biting insects that we all love. While we may not like all the gnat’s, mosquitoes, fly’s, etc., biting us but there are plenty of other animals that look forward to this time since for them it is a feast, this includes

• Birds - from swallows to hummingbirds

• Amphibians and reptiles - like frogs and toads

• Arachnids - including garden spiders and my favorite - jumping spiders

• And, most importantly for this post, Bat’s

Bat’s, like most animals, communicate through vocalizations. The difference with bats is that many of the vocalizations they make are beyond the range that we can hear (many of their calls are in the ultrasonic range).

In this project I’ll be using different techniques to convert ultrasonic bat calls from ultrasonic frequencies down to frequencies that we can hear. Human hearing range extends from 20Hz up to 20kHz (if you are young), but bat vocalizations extend from 12kHz up to 160kHz.

The main goals of this project are to:

• listen to bats

• locate bats\

• identify bat species

There are 2 main methods used to convert ultrasonic bat calls to frequencies within our range of hearing.

• The First approach uses the heterodyne method. This involves combining an internal reference frequency with a detected sound. The output that you her is the difference between the two frequencies. A simple example concerns a 42kHz bat call. The heterodyne technique would compare the call to a 40kHz reference frequency and the audible output would be a 2 kHz tone

• The Second approach divides the detected frequency. Using this technique the frequency is usually divided by 16 – so a 42kHz bat call would come out as a 2.6kHz tone.

Each method has it’s pro’s and con’s. Before we can look at them I’ll first have to get the circuits working. Which I hope to show in the next post.

Fungus is Amongus

Over this this past year I’ve developed a renewed interest in mycology. This current experiment developed out of my renewed interest and my continuing fascination with mycology.

My current experiment involves growing Blue Oyster Mushrooms indoors using the Monotub technique adapted for use with sawdust as a substrate (growth medium).

This video summarizes the procedure and technique for setting up a Monotub (The Complete Monotub Tek Cultivation Walk-through 

I have seen oyster mushrooms grown on manure compost in Monotubes or in bags of sawdust or straw as well as outdoors on hardwood logs.  Since I have no access to a yard and since I have used the Monotub technique in the past I'm hoping that it will work with using sawdust as a substrate (growth medium).  I haven't seen anyone else growing them on sawdust in a Monutub and there may be good reasons for this though I haven't come across any yet.  Keeping my fingers crossed.

I am using standard storage containers, like in the video linked above.  For the growing medium I am using 10 cups of hardwood sawdust pellets, 2 1/2 cups wheat bran, 9-10 cups of spring water along with 1/2 of a 6lb bag of grain spawn. All of this was mixed up by hand in a 5 gallon bucket and transferred to one storage tub.  I repeated the process for the second tub.  

tubs with sawdust and spawn

Pictures at 5 days after inoculation.

tub fully colonized with mycelium

After 5 days I added a layer of casing, about 1 ½ inches of coconut husk fiber hydrated to “field capacity”.  "Field capacity" means that when you squeeze a handful of the material you should get a drip or 2 of water out.  Oyster mushrooms will fruit without a casing layer being added, unlike many other mushrooms.  I added the casing layer specifically to help maintain moisture and humidity levels within the tub.

Prep for adding casing layer

 

After adding casing layer

Now that the mycelium has fully colonized the sawdust substrate and I've added a casing layer of hydrated coconut fiber it is time to ensure correct conditions for fruiting (the fruit being a mushroom).

The most important environmental considerations in growing mushrooms are: light exposure, ventilation/air changes, humidity and temperature.  Each type of mushroom requires different conditions.  I've listed the specifications for "fruiting" for Blue Oyster Mushrooms in the chart below (this is a compilation of information from different sources and is not meant to be exact).

The simplest way to maintain these conditions is to open the tubs and use the lid to fan them several times a day along with using a mist sprayer to add water after each ventilation while keeping them in an area that is the correct temperature.

My next Fungal post will address controlling these conditions using sensors and micro-controllers.

The main supplies that I've used in this experimental test are listed below:

North Spore

• 10lbs Hardwood sawdust pellets

• “Harbor Blue” Pleurotus ostreatus (discount grain spawn)

Local hardware store and grocery store

• 2 gallons spring water (Ice Mountain)

• wheat bran (Bobs Red Mill)

Further information on growing Oyster Mushrooms can be found all over the internet.  A few reputable sources are listed below:

https://extension.psu.edu/cultivation-of-oyster-mushrooms

https://smallfarms.cornell.edu/projects/mushrooms/indoor-production/

Project Shocker/Zapper Training Knife

(This is a potentially dangerous device so home experiments are not recommended - it is far safer to use commercial products that have been tested and certified as safe).

I wrote this up a few years ago and it is still on my back burner as something that could be a useful training tool.

Having an extensive background in fitness training and martial arts (especially Filipino and Thai martial arts) I was exited to see a very useful training on Hack Your Brain - the ShocKnife.  In the past I've used wooden blades, foam blades, aluminum training blades, rubber blades and even ratan blades (while wearing padded armor) and even real (live) blades when doing drills.  I've always been concerned since it wasn't always obvious if I'd been hit and so was the training/sparring I was doing effective?

The ShocKnife seems to solve this, or at least makes it more difficult to ignore that you've been tagged in some way.  Seeing it, I really want one (or better yet 2 for sparring) but at a price tag of $200 each it is unlikely.

After some searching I found that a few other people made attempts at DIY versions:
https://fightsciencesresearchinstitute.wordpress.com/2011/08/29/diy-electric-training-knife/
http://www.martialmakers.com/?p=89

Seeing these attempts, and looking at the actual specifications of the ShocKnife I can see a few issues:

• total power delivered
• current delivered
• voltage delivered

For safety we need minimal current levels (even 30mA can kill at the right voltage level).
Voltage needs to be high enough for the shock to get through clothin.

Looking at the commercial product ShocKnife the StressBlade is their entry level trainer and the specifications they list are 

• 7500Volts, less than 1mA (7.5kV at 0.75mA which comes to 5.625Watts of Power.

Reviewing the Specifications of the Fly Swatter Racquet and a standard commercial Stun gun.  Before I reveal the actual specs I will say that both of these devices, without alterations, can produce burns and other injuries - the ShocKnife seems to not do this.
Specs

• BugZapper Raquet - 2AA bateries (3V) seem to be a few hundred volts (maybe in the thousands) - with a high milliamp output
• Stun Guns seem to use 100,000's to 1,000,000's Volts at a few milliamp's and the ones used by law enforcement can cause significant burns
  

For a DIY solution we definitely need to ensure a very low current output but at an output frequency that is irritating while being harmless to human tissue.

I am still quite tempted to just purchase one of the commercially available StressBlade.  It isn't something I actually need for training but just something I feel would add to knife defense training.

Resources:
Shocknife
Voltage Multiplier Design Guide

Multiple Project Updates Coming Soon

I've been working to update a number of projects that have been sitting on my to do shelf for way to long.  In the next few weeks I'll be doing write ups on the following:

• Rebuild of my 12kV (~900Watt) Spark Gap Tesla Coil (Old Sparky). Mainly a build of a new DIY low inductance High Voltage capacitor that should allow for better resonance and energy transfer (and bigger arc's).
  
  
  
• My DRSSTC build using OneTesla parts - I couldn't afford the complete OneTeslaTS kit so many of the parts I've fabricated on my own.
  
  
  
  
  
  
• Further work on my Voight Kampff machine - its been a long break but I'm back at it