hi,
I need any suggestion for rectification of a 100mV signal for energy harvesting purposes. I am getting a signal with peak to peak amplitude of roughly 90mV to 120mV and the current is around 4-5 mA range. I would like to rectify that, any suggestion? is this even possible?
(I am generating this power using a micro sized mini hydraulic generator.)

thanks

 

There is a circuit known as a precision rectifier

https://en.wikipedia.org/wiki/Precision_rectifier

that uses an opamp. You may or may not be able to adapt it for your purposes. My guess is that the opamp will require more power than you can ever extract from your source. This is the nature of what you are trying to do. IMHO it is an utter, absolute, and complete waste of time. If you're young and have time on your hands to burn, then by all means -- go for it.

 

hi,
I need any suggestion for rectification of a 100mV signal for energy harvesting purposes. I am getting a signal with peak to peak amplitude of roughly 90mV to 120mV and the current is around 4-5 mA range. I would like to rectify that, any suggestion? is this even possible?
(I am generating this power using a micro sized mini hydraulic generator.)

thanks

Have you surveyed the available energy harvesting ICs? The capabilities of those ICs will give you a good idea of where the star-of-the-art is. My hunch is that 100mV is near the bottom and would be very difficult to use for power.

In the course of thinking about this topic and typing these words on my laptop, I've used more power than this device will capture in a lifetime.

 

Google "energy harvester IC".
But, as noted, the signal energy is only about 500μW, so you are not going to power very much with that.

 

Unfortunately there is a realistic bottom end in practicality to energy harvesting. When your voltage is under 1 volt and the current is only a few milliamps there is a very limited amount of applications for such a source to begin with.

Your time, effort and money is better spent on making the power capturing/generating end of the system bigger to the point it can at least compete with a single cell 1.2 or higher voltage battery.

 

There is a circuit known as a precision rectifier

https://en.wikipedia.org/wiki/Precision_rectifier

that uses an opamp. You may or may not be able to adapt it for your purposes. My guess is that the opamp will require more power than you can ever extract from your source. This is the nature of what you are trying to do. IMHO it is an utter, absolute, and complete waste of time. If you're young and have time on your hands to burn, then by all means -- go for it.

The output of the Precision rectifier comes from the opamp supply and not from the input source signal.

 

Yep, it appears that 100 mv is the lowest you can go right now.

Texas Instruments: Overview for Energy Harvesting & Solar Charging

 

Hello,

You could have a look at the LTC3107 or the LTC3108.
http://www.linear.com/product/LTC3107
http://www.linear.com/product/LTC3108

Bertus

 

The output of the Precision rectifier comes from the opamp supply and not from the input source signal.

You asked if there was ANY way to do rectification at a voltage below the normal threshold of of a pn junction diode. Reread my post carefully; I said: "You may or may not be able to adapt it for your purposes". I'm no expert in energy harvesting, and I never plan to be one because I believe it is a complete wast of time. So take my suggestions or don't take them -- I don't care; but don't complain because I don't know all of your requirements and constraints from a three sentence post about what you want.

 

@Papabravo: No, no, not complaining at all. I am not the OP either.
I did not find any reference to pn junction diode in the OP's post, it may have been edited, though.
I saw 'energy harvesting purposes' in the OP's post, and thought would mention it.
I appreciate your time helping people, and enjoy the forum. I never meant to comment to elicit such a response.

 

I like the 100:1 transformer

 

@

Hello,

You could have a look at the LTC3107 or the LTC3108.
http://www.linear.com/product/LTC3107
http://www.linear.com/product/LTC3108

Bertus

I like the 100:1 transformer

Thanks guys! I have a question. I am getting the energy from a mini hydraulic generator (technically I am using a reverse stepper motor to convert mechanical energy of blade rotation to the power) and I am getting some sort of fuzzy AC signal out of it. Can I still use this chip and input my signal to it? I was not sure because it seems that this IC is originally made for peltier cells (I have never worked with peltier cells but I am assuming that peltier cells generate DC output and this chip is manly a DC to DC step up? am I correct? will it work with my fuzzy AC signal?).
thanks again.

 

Thanks guys! I have a question. I am getting the energy from a mini hydraulic generator (technically I am using a reverse stepper motor to convert mechanical energy of blade rotation to the power) and I am getting some sort of fuzzy AC signal out of it.

Either its not a working stepper motor or its being turned unnessarily slow being most any basic stepper motor will easily produce a volt or more at several 10's of RPMs or more which with common low forward drop germanium diodes is plenty enough voltage to work with.

Also, most stepper motors are biphase so it should have four or six leads coming out of it to work with that all produce AC current when the motor is being spun.

 

hi,
I need any suggestion for rectification of a 100mV signal for energy harvesting purposes. I am getting a signal with peak to peak amplitude of roughly 90mV to 120mV and the current is around 4-5 mA range. I would like to rectify that, any suggestion? is this even possible?
(I am generating this power using a micro sized mini hydraulic generator.)

thanks

Yes....look up "absolute value amplifier".

 

@Papabravo: No, no, not complaining at all. I am not the OP either.
I did not find any reference to pn junction diode in the OP's post, it may have been edited, though.
I saw 'energy harvesting purposes' in the OP's post, and thought would mention it.
I appreciate your time helping people, and enjoy the forum. I never meant to comment to elicit such a response.

I didn't see it as a complaint but I anticipated that comment when I suggested that a precision rectifier could do what the OP/TS asked, but it might not be suitable for "energy harvesting purposes". The OP/TS mentioned rectification in the title of his post and later in the body as well. I supposed there might be such a thing as an ultra-low power opamp that could be used in this application, but it has been almost a decade since I had to pound the datasheets.

 

Just as an aside, I recall reading some time ago about someones proposal to generate power using MANY thermocouples and using the temperature difference between the cold ocean bottom and ocean upper layers. I believe the idea was to float a HUGE array of these TCs with the top connection at ocean surface and other connection at ocean bottom.
I guess theoretically it could work. Don't know how practical it would be!

 

Just as an aside, I recall reading some time ago about someones proposal to generate power using MANY thermocouples and using the temperature difference between the cold ocean bottom and ocean upper layers. I believe the idea was to float a HUGE array of these TCs with the top connection at ocean surface and other connection at ocean bottom.
I guess theoretically it could work. Don't know how practical it would be!

The First Law of Thermodynamics shows how to get work and heat from internal energy. The Second Law of Thermodyanics and conservation of energy make getting work from heat impossible.

 

...The Second Law of Thermodyanics and conservation of energy make getting work from heat impossible.

Maybe impractical, but not impossible as long as you have a ∆T gradient.

 

Maybe impractical, but not impossible as long as you have a ∆T gradient.

That's why they make chocolate ice cream.