Small transmitters for small signals?

[Mokele]

Ok, I'll preface this by saying I know almost nothing about electronics, except the bare minimum I'm picked up fro Physics 2 and working with various things at the user level.

 

Anyhow, a bit of background: I'm going to be doing experiments soon involving electromyography, the detection of electrical impulses in muscles to tell when they're active. Specifically, I'll be working with snakes, on locomotion. Now, our current setup has direct wiring, in that the wires go from the snake to the little screw-down connector thingys (told you I was bad at electronics) to the amps, etc, which means the length of the wires constrains the motion of the animal.

 

What I'm wondering is this: Is there some sort of cool transmitter-type thing which I could use instead, so the input signal could be sent to a reciever (thus giving the animals more freedom of movement)? The input signal is from 2 wires, and is basically random fluctuations in the microvolt range (hence why we have the huge set of amps) that vary in amplitude (we look for the places where the amplitude massively increases, indicating activity). Any sort of transmitter would only need a range of about 12 feet, but would need to be a) cheap b) without a wire for power supply (since that would eliminate the benefit of a transmitter at all) and c) small, by which I mean under a gram in weight, ideally, though any sort of potential device in that size range would be great.

 

I realize the size is probably going to be the most difficult part, but the problem is that things that are too big will seriously alter the animal's locomotion. A 16 gram object is 10% of the total body mass of some of the these animals. On the other hand, any huge equipment on the receiving end would be fine.

 

So, basically, is this sort of thing even possible? Is it feasible? If yes to both, where should I go to learn how to make these things?

 

Mokele

[Douglas]

Specifically' date=' I'll be working with snakes, on locomotion. Now, our current setup has direct wiring, in that the wires go from the snake to the little screw-down connector thingys (told you I was bad at electronics) to the amps, etc, which means the length of the wires constrains the motion of the animal.

 

What I'm wondering is this: Is there some sort of cool transmitter-type thing which I could use instead, so the input signal could be sent to a reciever (thus giving the animals more freedom of movement)? The input signal is from 2 wires, and is basically random fluctuations in the microvolt range (hence why we have the huge set of amps) that vary in amplitude (we look for the places where the amplitude massively increases, indicating activity). Any sort of transmitter would only need a range of about 12 feet, but would need to be a) cheap b) without a wire for power supply (since that would eliminate the benefit of a transmitter at all) and c) small, by which I mean under a gram in weight, ideally, though any sort of potential device in that size range would be great.

 

I realize the size is probably going to be the most difficult part, but the problem is that things that are too big will seriously alter the animal's locomotion. A 16 gram object is 10% of the total body mass of some of the these animals. On the other hand, any huge equipment on the receiving end would be fine.

 

So, basically, is this sort of thing even possible? Is it feasible? If yes to both, where should I go to learn how to make these things?

 

Mokele[/quote']It seems to me that these two wires must be a transducer of sorts that converts small movements (perhaps acoustic or acceleration) to volts (microvolts in this case). Do you know if this is the case? NOTE: There are numerous transducers E.G. microphones, antenna's, dissimilar metals (for temperature), crystals etc.....so for starters, we need to know about the wires.

 

Then, after the impulses (signals) are amplified, has anyone looked at the output on a scope??

[Mokele]

It seems to me that these two wires must be a transducer of sorts that converts small movements (perhaps acoustic or acceleration) to volts (microvolts in this case). Do you know if this is the case?

 

Actually, it's just the bare ends of two wires. The trick is to implant them into the muscle (the wires are *very* thin, and this is done under anaesthesia, so the animal doesn't feel any pain). Each barb will be located in a different muscle cell, and the cells depolarize (like a neuron) when they contract. Thus, the equipment reads the differences in voltage (intra-cellular ion concentrations) between the two cells, resulting in a large (if messy) amplitude jump when the muscle contracts.

 

Then, after the impulses (signals) are amplified, has anyone looked at the output on a scope??

 

That's part of the end set up, after the amplifiers, along with a host of complicated stuff that synchronizes it with high-speed video and records the 13 channels we have.

 

Basically, I'm after a wireless, lightweight way to get the signal from the snake to the rest of the equipment, so the wires don't constrain movement anymore.

 

Mokele

[Douglas]

Basically, I'm after a wireless, lightweight way to get the signal from the snake to the rest of the equipment, so the wires don't constrain movement anymore.Mokele

Yeah, I know what you're looking for, I was just trying to get a feel for the type of "pickup" you had, and the frequency range of the device.

 

Not knowing this, I'll throw a couple of things on the table. Yes, the device you're looking for can be designed.

The two bare wires sound inefficient to me. My wife has a pedometer with a heart rate monitor, it's a tranducer, the size of a dime, place your finger on on it and it has enough amplification to emit a loud beep with each heartbeat, probably enough power to transmit a foot or two (depends on the sensitivity of your receiver....cost $22.00 at radio shack....size, probably about 4 dimes stacked.

Other amplifiers/transmitters...a hearing aid...40 to 60 dB of gain...$11.00 on the internet. Polygraph machines have a number of transducers that could probably be obtained cheap.

[Mokele]

The two bare wires sound inefficient to me.

 

Well, the wires aren't bare along their whole length, just at the tips that poke into muscle tissue. Because of the anatomy of the system, we can't make use of less invasive techniques that don't directly measure particular individual muscles.

 

My wife has a pedometer with a heart rate monitor, it's a tranducer, the size of a dime, place your finger on on it and it has enough amplification to emit a loud beep with each heartbeat, probably enough power to transmit a foot or two (depends on the sensitivity of your receiver....cost $22.00 at radio shack....size, probably about 4 dimes stacked.

Other amplifiers/transmitters...a hearing aid...40 to 60 dB of gain...$11.00 on the internet. Polygraph machines have a number of transducers that could probably be obtained cheap.

 

Thanks!

[calbiterol]

This is a little out of my league, but you could, concievably, use a cheap wireless microphone for the job - the circuitry in them is really small, it's the diaphragm that's big and heavy. The power source there, unfortunately, is often a 9v. Now, in theory, you could supply all the power you wanted through induction (just like the chargers on electric toothbrushes - induced current - put it in the surface where the snake is "locomoting" ) but not only is that a bit overboard, it'd probly interfere with equipment. Anyways, you could also convert the electrical impulse to audio - you could use ultrasound, and then have a ultrasonic sensor to give your equipment a data feed. Or, you could pick apart any number of simple devices. You could probably rig up the insides of an electronic remote (a.k.a. zappers, space command, clicker, tv-thingy, et cetera, ad infinitum, ad nauseum) to send the signal, and that would be light. As far as actually going about doing it, I could probably tell you how if I had a model number, etc - I'd just rig it up myself, and then explain the process - but it's much easier for me to just do it that explain a hypothetical situation. Wow, am I babbling or what!

 

Hope that helps.