1mv peak to peak wave generator

[tacHammer]

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

 

[Roff]

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.

 

[dknguyen]

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.

 

[tacHammer]

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.

 

[Roff]

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).

 

[tacHammer]

Ha! You are so right. Correction apprecaited. 65-70bpm is what I meant not 65-70hz. Sorry.
Rick

 

[Roff]

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?

 

[tacHammer]

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

 

[Nigel Goodwin]

Just use a 555 timer to generate your signal, then a simple resistive attenuator to drop it down to 1mV.

 

[pc88]

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

Thanx for your reply.

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

 

[tacHammer]

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.

 

[pc88]

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?)

 

[Roff]

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.

 

[tacHammer]

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.

 

[KMoffett]

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

 

[Roff]

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.

 

[tacHammer]

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:

 

[tacHammer]

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.

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.

 

[Roff]

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.