• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Modifying a spy microphone for leopard conservation

Status
Not open for further replies.

kra

New Member
Hi everyone,

I'm looking to attach a spy microphone to leopard radiocollars and have it record continuously for 1 month.

Why? Well, for my project I'm looking at whether strategically played competitor sounds could be used to manipulate leopard movements in order to reduce conflict with people. But I need to know how vocals naturally affect their movements.

I'm looking to hack the EDIC-Mini-Tiny B47 microphone so that it connects to a power source that powers it for 600 hours (its storage capacity). It's current battery life is up to 168 hours.

I'm out in the African Bush right now, and so I would need to know whether this hack is possible and, if so, would be looking to team up with someone who can advise me on how to make the modifications.

Weight is a major limitation here, and I would need a battery solution which weighed < 75g.

Price is also an issue as the project budget is already stretched. So, I would be looking for a battery solution which was preferably < $50 (although, higher priced options would be considered).

Can anyone help?

Thanks,

K.

Disclaimer: I am an electronics newbie and internet access here is limited, but I am a keen learner.
 

Attachments

mdorian

Member
Hi K
Two AA alkaline batteries in parallel will have have around 50 g weight and 4000 mAh capacity (the battery you use has at most 700mAh) , it should be enough. Take care if you are in a rainy environment , the device is for indoor use you should protect it somehow in a protective case. Do not use the included battery because it needs air to work and you cannot waterproof your device properly.
 

alec_t

Well-Known Member
Most Helpful Member
Looks like the hack would be straightforward if you are able to engineer a dummy battery to make contact with the circuit.
On the subject of waterproofing, have you tested the microphone sensitivity when it's covered by a protective film?
 

kra

New Member
Hi MDorian, Alec,

Thank you for your messages and advice.

It does sound straightforward.

I did a quick google and found a few different sets of instructions on how to make dummy batteries.

So, would the 2 AA batteries in parallel output the same power but just over a longer period (since the capacity is bigger), or is there a danger of it damaging the circuit because there's more power in them?

I haven't tested the microphones sensitivity myself, but a previous study on chipmunks used the B47's predecessor and tested the sensitivity of the microphone when in a protective film and found it was still very good (it could detect the chipmunk's heartbeat when they were at rest). They described the steps they took to weatherproof the device, and I was planning on just following the steps and then attaching to a new power source.

Cheers again,

K.
 

audioguru

Well-Known Member
Most Helpful Member
Some people replying cannot read. The mic uses three tiny G13A silver oxide button cells, not two and they are probably in series, not parallel. It is easy to see if they are in series.
AA batteries are many times larger and heavier and will be overkill.

Energizer battery company says that their 357 battery cell is a G13A and supplies 0.221mA for 600 hours when its 1.55V begins to drop. Since they last only 160 hours then the current is probably 600/160 x 0.221mA= 0.83mA or maybe 1mA.
I could not find any button cells large enough so use three AAAA or N alkaline cells.

A product uses only as much current as it needs when its supply voltage is correct. A car battery can supply 600A to start an engine when it is cold but the clock uses the same battery at a current of 0.01A or less. Two or three AA cells in parallel produce 1.5V when they are new. Three cells in series produce 4.5V. If the mic needs 4.5V but you provide only 1.5V then it will not work.
 

alec_t

Well-Known Member
Most Helpful Member
4.5V is clearly the present and recommended supply voltage, but it might be worth experimenting to see if you can get good results using only 3V. If you can, then a single lithium cell (nominally 3.6V, but usable down to 3V) could give a weight saving.
 

mdorian

Member
Mea culpa for the reading but "some of us" are missing the fact that a g13 zinc-air battery has the same capacity (600mAh) as one AAAA battery. The capacity needed is 3 or better 4 time higher around 2000 mAh , that would be 9 or 12 AAAA batteries each at least 7g , to much for the specifications. Maybe a 18650 li-ion rechargable battery , 45g up to 3000 mAh. 3.6 to 4.2V (if the g13 batteries are connected in series which is most likely ). Or maybe recycling a li phone battery?
 

audioguru

Well-Known Member
Most Helpful Member
The silver oxide button battery cells the mic comes with have an absolutely flat voltage at 1.55V to 1.5V while discharging until near the very end. If the mic still works well with a total battery voltage of 3V or 3.6V then they would have used cheaper and more common alkaline button cells.

Hey! There is a leopard outside and is coming to my door. Nope, it is my wife in her new leopard patterned leggings.
 

mdorian

Member
160 hours is for a 600 mAh zinc-air battery . The same size silver-oxide cell have a capacity of 200 mAh , an alkaline battery 150 mAh. The zinc-air battery have a flat voltage of 1.28V. I don't think the voltage was the reason , the capacity is slightly higher on silver-oxide cells that looks better in the datasheet.
Let's see pro's and con's for each option:
- zinc-air cells 3x4 series-parallel , 12 pcs , total capacity4x600 = 2400 mAh , total recording time 4x160 = 640h weight 2.3x12= 28g
pro: lightweight , high capacity
con:- needs air to work which can make waterproofing dificult, must be used after removing the seal.
- alkaline AA bateries capacity between 1800mAh and 2600 mAh , 2400 a good one ,3 in series recording time 4x160 = 640h , weight 23gx3=69g
pro: cheap
con: the weight is at the upper limit, linear discharge graph with low voltages at the end.
- 18650 li-ion rechargeable, battery45g up to 3000 mAh, let's say 2400 mAh ,3.6 to 4.2V voltage. Weight 1x45g , total recording time 4x160 = 640h.
pro: high energy density , appropriate voltage , can be reused.
con: needs a charger which can go over the budget , special cautions must be taken, an electrical short can make them explode so it needs a good mechanical protection.
 

kra

New Member
Hi all,

Thank you very much for your messages. Great advice - I understand now that mAh informs the capacity I need as it tells me how much the recorder uses per hour.

I seem to have found a recording module by the same company that allows for more storage capacity and connection to an external battery source.

I'm having trouble interpreting the main technical characteristics of the device in terms of the volts needed and how many mAh the device will use when recording. To me, there seem to be several characteristics that fit the bill.

I've attached the link to the manual (page 5) below; could anyone please help me interpret the voltage required and the mAh use?

Also, definitions of 'consumption current' (why is it in V), 'supply voltage' (why i it in mA), and 'input signal' would be great.

Apologies for the above requests, I would normally google, but internet access is poor out here and keeps crashing.

Thanks again,

K.

http://www.ts-market.com/upload/iblock/958/eng_emm tiny.pdf
 

mdorian

Member
Also, definitions of 'consumption current' (why is it in V), 'supply voltage' (why i it in mA), and 'input signal' would be great
You're right , it's a mistake supply voltage is 3V and consumption current 2mA.
Unless you really have some skills for electronic circuits I would stick to the first option. This one is only a recording module , you will need to attach a microphone , an low signal amplifier and a voltage regulator. The power consumption just looks better , for the same battery the recording time would be 600mAh/2mA = 300 hours but this is for uncompressed audio which will use a higher amount of memory.
 

kra

New Member
Thanks for your message and advice. That makes sense.

The reason that I really wanted to go for the recording module is because of the storage capacity. The 32 GB model can store 720 hours of uncompressed audio at the sampling rate I want, whereas for the first option I would only get 240 hours or would need to use a 2-bit ADPCM compression.

I will ask around and see if there are any collaborators here who could help me modify the second option; if not, I will stick with the first option.

Cheers,

K.
 

alec_t

Well-Known Member
Most Helpful Member

kra

New Member
Hi Alec,

I contacted the manufacturer and they told me they have a 32 GB model and provided me with the recording times under the different compression methods.

Cheers,

K.
 

Tony Stewart

Well-Known Member
Most Helpful Member
Zinc air (with suffient air and no moisture problems) has the highest consumer battery power/weight or volume density. Although expensive at $100/ kWh, your choice is limited by budget, size weight so, increasing all of the above in the same battery technology works far better than Alkaline or even LiPo.

However if degradation is factored by weather or cost, certain LiPo types with manganese may be a possible solution.

Your objective needs to be defined in terms of Cost/kWh, Voltage, Volume and weight.
Please define your limits.

https://en.wikipedia.org/wiki/Comparison_of_battery_types#Common_characteristics
 

Tony Stewart

Well-Known Member
Most Helpful Member
I think the smarter solution is to have a secondary mic and microchip that acts as a selective trigger to conserve the main power draw of the recorder. This might be done with a few mA and a selectric mic bonded to the main mic and some convenient trigger power interface cable.

Then with VOX control , you can possibly extend your recording life by an order of magnitude or two. Noise gating is fundamental with the trigger design.

Consult with factory.
 

Tony Stewart

Well-Known Member
Most Helpful Member
As every seasoned Engineer knows, the best result starts with a clear list of all the rquirements in your mind . Take for example how to trigger a complex waveform and choosing how to trigger by filter and trigger attributes;

such as: source S/N ratio, LPF, HPF, BPF, DC,AC +,-, delay, duration, sampling rate.

An expert Engineer can convert your detailed verbal descriptions into these characteristics to optimize the trigger and event recording.

Capiche?
 

audioguru

Well-Known Member
Most Helpful Member
The recorder has a Voice Activation system (VOX) to extend its memory and probably also extend its battery life so maybe you must teach the leopard to say the password since the recorder also has Password Protection.
 

Tony Stewart

Well-Known Member
Most Helpful Member
The recorder has a Voice Activation system (VOX) to extend its memory and probably also extend its battery life so maybe you must teach the leopard to say the password since the recorder also has Password Protection.
audioguru good one!

My GPS has keyword recognition for Search menu and contents, with clear background and dialog, sometims I Get perfect results and others not even close, or false triggers from the radio for three syllables.

The false positives and false negatives on VOX recognition vary greatly with SNR and cadence ( with little or no gaps in words).

If only the OP could consult the factory for a solution or ask http://www.LOTEK.com near me. Use my name for a finder's kudo.
 
Last edited:
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top