1mv peak to peak wave generator

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tacHammer

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I'm looking to build a simple 1mv peak to peak square or sawtooth generator that will fit in my shirt pocket. I'd like the frequency around 65hz. Should I use a timer or does someone know of something simpler?

Any help will be appreciated.

tacHammer
arklamed@sbcglobal.net
 
I'm just curious why you would want a 1 millivolt signal generator.
 
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Can you just generate a regulator wave, step it down with a resistive divider buffered by an op-amp buffer followed by a AC pass capacitor (to remove offset from the op amp, since 1mV is pretty damn small compared to the mV-order offsets on most op-amps). 65Hz is really slow so I would think a capacitor timer, like a 555 timer would be best.
 
Roff said:
I'm just curious why you would want a 1 millivolt signal generator.

I want this for a simple ECG simulator that will fit in my pocket. 1mV peak to peak is about the normal size and 65-70hz would be perfect to test telemetry transmitters. The waveform doesn't have to look like an ECG. It wouldn't matter if it was a square wave or a triangle wave.

Pocket sized ECG simulators cost $1,400.00 and that's not an affordable option.

Thanx for your reply.
 
Is that the required bandwidth of an ECG channel? It's about 60 times a normal pulse rate (60-70 beats/min).
 
Is this a one-off, or do you need a robust design that doesn't require any adjustments? Does it need long battery life? Can you use surface-mount parts, or do you need to use common thru-hole parts?
 
Roff said:
Is this a one-off, or do you need a robust design that doesn't require any adjustments? Does it need long battery life? Can you use surface-mount parts, or do you need to use common thru-hole parts?

If I had a unit that is small enough I can deal with it not being adjustable. I just need something simple that will run around 60-70bpm. Battery life is not important. I'm not sure that I would be able to use or solder SMD's with my eyes that are over 50 years old. (c: I'd prefer thru-hole parts.

Thanx,
tacHammer
 
Just use a 555 timer to generate your signal, then a simple resistive attenuator to drop it down to 1mV.
 
pc88 said:
Why are they so expensive? Do they do anything else besides generate a 1mV 1 Hz square wave?

Update: Here's one that's a bargain at only $250:
https://www.ecgsimulators.com/prod02.htm


Thanx for your reply. What you can't see in that photo is the unit is laying down and is much larger than it appears in that picture. I have a simulator that is smaller than that one but what I want is one that will fit in my shirt pocket.
The $1400 unit will do much more than just emit a 1mV wave at 60-70bpm. You can adjust it from 30 to 120bpm and from .5mV to 2mV and it even has arrhythmias built in. I have a simulator that can do all that if I need it but I just want something that can simply use to test whether a telemetry transmitter is working or not by putting a waveform on the central station monitor.

If I wasn't so lazy and hairy chested I could just put electrodes on myself.
I guess that's what I should consider.
 
Sounds like this is an opportunity for a uC project. The size would only be determine by the user interface (leds, buttons) and connectors and the battery. Hmm.... (can you hear the wheels turning?)
 
Here's a 555 circuit, like Nigel suggested. It should run on a couple of AAA's for months (years?).
There are several CMOS 555 models - TS555, LMC555, ICM7555, ZSCT1555, etc.
 

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Roff said:
Here's a 555 circuit, like Nigel suggested. It should run on a couple of AAA's for months (years?).
There are several CMOS 555 models - TS555, LMC555, ICM7555, ZSCT1555, etc.

That's perfect! Thanx Roff.
 
tacHammer,

From a former Biomed Tech...a LM555 EKG simulator was a project I built in my Medical Electronics class back in 1974. What goes around comes around.

Ken
 
tacHammer said:
That's perfect! Thanx Roff.
You're welcome. Most of the responses here for circuit help (and I do this myself sometimes) are of the form, "you can use one of these IC's". If you're lucky, someone will post a schematic they had laying around, or they found on a web site, of something that you could modify, or they point you to a tutorial. These responses are good if the OP has some circuit design skills, or wants to learn some. Lots of guys, though, and I suspect you are one of them, just want a schematic they can build that will work. They're trying to solve a problem, and don't give a hang about learning how to do it themselves. For these guys, it sometimes only takes 10 or 15 minutes to crank out a simple design, and even simulate it for insurance. This was one of those times.
 
KMoffett said:
tacHammer,

From a former Biomed Tech...a LM555 EKG simulator was a project I built in my Medical Electronics class back in 1974. What goes around comes around.

Ken

I'm still a bio-med tech but haven't built a project in many years. (c:
 

Haha, Roff you got me pegged! I'm over 50 and too tired, busy and forgetful to design my own circuit so I really appreciate your assistance.
 
tacHammer said:
Haha, Roff you got me pegged! I'm over 50 and too tired, busy and forgetful to design my own circuit so I really appreciate your assistance.
I'm 66 and retired, and I suspect that staying active in electronics (with this forum being a big part of that) is what is staving off mental old age. My body is having a tougher time of it.
 
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