I tried quantifying the accuracy and noise of the redesigned dynamic clamp circuits (see September 2019 update and the CircuitLab tab). Here is a document describing what I found (Accuracy_and_noise). TL/DR: The new designs may eliminate the need for calibrating the system and generally make the system more accurate and less noisy.
I finally started writing a description of the new and improved circuit designs that I mentioned in my July 2019 update and that are shown in the CircuitLab section of this site. Here is a link to a draft version of a new methods section: Draft_of_revised_methods_100219 . Once I finish editing that, I will revise the construction section to reflect the new designs. Any comments on or suggestions for the draft methods section would be much appreciated.
I have been working on a somewhat improved hardware design that: (1) uses a 3.3 V voltage regulator to provide a reference voltage for the circuits of Figures 2B and 2D rather than relying on the output of the rail splitter for this purpose (the rail splitter continues to provide the ± 9 V needed to power the op-amps), (2) rearranges the resistors so that it is simpler to find values that will capture most of the dynamic range of the amplifier and/or digitizer, and (3) provides protection for the Teensy and other electronic components in case of an accidental overvoltage (e.g., connecting a 100x gain amplifier to a circuit meant for a 10x gain amplifier). The main advantage of these changes is that, by using a stable and (relatively) exact 3.3 V as the reference, imperfections in the 18 V power supply (“wall wart”) and some of the other components don’t matter as much. In fact, the system may not need calibration at all.
I haven’t written up the changes yet, but for those who like electronic circuits, you can find the designs in the CircuitLab section, indicated in the menu. As the name suggests, each of the designs has a link to a CircuitLab simulation (www.circuitlab.com), so that you can test how it works.
If you are interested in the these new circuit designs but run into trouble in making them, please do not hesitate to write to me. — Niraj Desai (email@example.com).
Added a section (dyClamp & pyClamp) with a description of and links to a software project by Christian Rickert (GitHub) that (1) provides an alternative Arduino sketch with robust serial communication between microcontroller and host computer (dyClamp) and (2) a Python interface to control simulations (pyClamp).
Added a Media section to hold videos and pictures.
Refined the description of the calibration procedure and edited the associated Processing sketch (processing_calibration.pde); now measurements will be plotted as they’re being obtained.
Added a section (External or saved conductances) that describes how to send the Teensy microcontroller analog signals representing up to three separate conductance trains, so that the Teensy can inject these conductances into a neuron. A typical use case would be when an experimenter, having previously recorded excitatory and inhibitory synaptic currents in voltage clamp mode (perhaps in vivo or in culture), would like to feed conductances derived from these recordings into a different neuron (perhaps in a brain slice).
The added section also describes how to save conductance waveforms in the Teensy’s memory so that they can be read out element by element at run-time, rather than being generated by numerical integration.
Also added a section (Troubleshooting) which will include troubleshooting tips.