Tethered Headstage Voltages#
-The voltage on the headstage must be carefully regulated: if its too low the -headstage will not function reliably. If the voltage is too high sensitive -components could be damaged. Many issues with the system can be traced back to -inadequate headstage voltage supply.
+Headstage Voltages#
+Each ONIX headstage has a required operating voltage that is specified on its +documentation page. Because ONIX hardware supports headstages that have +different voltage requirements, it must be changed to match the requirements +of the headstage that is plugged into a port. If the headstage voltage is too +low, it will not function reliably. If the voltage is too high, the headstage +will dissipate excess heat and it may be damaged.
Setting headstage voltage#
-Each headstage has a minimum and maximum voltage requirement (e.g. 5.3 to 5.7 -Volts for Headstage-64) circuits on the board to function properly. If -the voltage is far too low, the green LED on the headstage will be dim and -Bonsai will not detect the headstage. Even if the LED is bright, a borderline +
Setting Headstage Voltage#
+The headstage voltage is set using FMC Link Controller devices +on the PCIe Host. Each headstage has a minimum and maximum voltage +requirement (e.g. 5.3 to 5.7 Volts for Headstage-64) in order for +circuits on the board to function properly. If the voltage is far too low, the +host computer will not be able to detect the headstage. A borderline voltage can still cause connectivity issues as the headstage occasionally dips -beneath the power it needs to function properly.
-The voltage output at the FMC-host can be set in Bonsai:
-
- Default headstage voltage is 4.9 V
+below the level it needs to function properly. +Attention
+The OpenEphys.Onix1 Bonsai package automatically sets the +headstage port voltage by default, but allows the user to override the +voltage setting as well. The documentation linked shows how to use this +functionality and what valid voltage ranges are for each headstage. This +functionality has been been tuned for the tethers that are shipped with each +headstage. The voltage override is available when custom tethers are used +(see Measuring Headstage Voltage).
- Increasing the voltage to 7V in Bonsai (measured as 5V at the headstage) allows the second headstage to connect.
-The voltage set in Bonsai is not identical to the voltage supplied to the -headstage, as some voltage drop will occur over the coaxial cable tether that -connects them. The amount of voltage drop will depend on the cable properties -(e.g. thickness) and even the temperature of the cable. These very thin tethers -can cause large voltage drops, so that even when the voltage setting in Bonsai -seems high, the headstage is only seeing 3 or 4 Volts and becomes unreliable. -Voltage should therefore always be measured on the headstage itself. The -voltage setting is persistent until computer power off. It gets stored in the -hardware, so even after a reboot, it will be set to the latest value.
+The voltage set in software is not identical to the voltage supplied to the +headstage, as some voltage drop will occur over the tether that connects them. The +amount of voltage drop is proportional to the current draw of the headstage and +inversely proportional to the thickness of the tether. The thin tethers used +with ONIX headstages can result in significant voltage drops that need to be +compensated for. For very long (5 to 10m) and thin (diameter of 0.2mm) coaxial +tethers, the voltage drop can be on the order of 2 volts. For this reason, the +headstage voltage must be measured on the headstage itself.
Measuring headstage voltage#
+Measuring Headstage Voltage#
Use a multimeter to probe the headstage at the two points marked below: the ground pin and either terminal of the large inductor on the headstage.