Re: [Emc-users] Current Sensors
I really prefer sensors made by these guys: http://www.lem.com These are the sensors used in a number of VVF drives used in high reliability applications. N.C. On 2012-Mar-18, at 13:00, Kirk Wallace wrote: These look pretty handy: http://www.pololu.com/catalog/product/1187 I'm thinking about ways to add load sensing for drives that don't have this feature yet. Also, I wonder if they are fast enough for PWM signal control? Digikey has some other models of these sensors but it seems for my purposes, the working voltage isn't high enough, or the current range is too wide and some resolution is lost. Current can also be measured with an opamp measuring voltage across a current sense resistor, but I'm worried about a common mode voltage in the hundreds of Volts. Is there away to handle this? -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_nov ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Current Sensors
On Sun, 18 Mar 2012, Kirk Wallace wrote: Date: Sun, 18 Mar 2012 10:00:19 -0700 From: Kirk Wallace kwall...@wallacecompany.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: LinuxCNC Users List emc-users@lists.sourceforge.net Subject: [Emc-users] Current Sensors These look pretty handy: http://www.pololu.com/catalog/product/1187 I'm thinking about ways to add load sensing for drives that don't have this feature yet. Also, I wonder if they are fast enough for PWM signal control? Digikey has some other models of these sensors but it seems for my purposes, the working voltage isn't high enough, or the current range is too wide and some resolution is lost. Current can also be measured with an opamp measuring voltage across a current sense resistor, but I'm worried about a common mode voltage in the hundreds of Volts. Is there away to handle this? Hall effect sensors are one way. They have the advantage of simplicity and not requiring floating power on top of the swited leg. TI makes some nice isolated current sensors (like the AMC1204) current sense resistors in the low side can also be used but the pair of resistors that are sampled and the exact sample time must be chosen carefully depending on the PWM waveforms (High side series sensors have the advantage the they dont see the switching only the ripple) -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Current Sensors
On Sun, 2012-03-18 at 10:15 -0700, Peter C. Wallace wrote: ... snip Hall effect sensors are one way. They have the advantage of simplicity and not requiring floating power on top of the swited leg. TI makes some nice isolated current sensors (like the AMC1204) current sense resistors in the low side can also be used but the pair of resistors that are sampled and the exact sample time must be chosen carefully depending on the PWM waveforms (High side series sensors have the advantage the they dont see the switching only the ripple) Thanks for your reply Peter. One application I am thinking about is sensing current in one of the motor leads from a KBIC SCR driver. I believe these leads float pretty widely from mains ground. The KBIC's internal current sense floats too, so there is no problem. I have a setup on the bench that uses an ATmega32 that runs Modbus, plus Speed PWM and bit I/O through opto-isolators. I'd like to add motor current to the Modbus reply data (motor voltage would be nice too), but the floating motor leads seem to be an issue. Thinking a little more, I suppose I could float the ATmega along with the KBIC and isolate the TTL side of the RS485 chip. This puts me into thinking about floating supplies. On the other hand, if one where to go to the trouble to put an AVR onto a KBIC, it would be better to just design a new DC motor drive based on the AVR, maybe. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Current Sensors
On 03/18/2012 10:00 AM, Kirk Wallace wrote: Current can also be measured with an opamp measuring voltage across a current sense resistor, but I'm worried about a common mode voltage in the hundreds of Volts. Is there away to handle this? You not only have to withstand the CM voltage, you have to have good CM rejection of many Mhz signals to avoid switching spikes on the current signal. Tough to do without opto or transformer isolation. Karl -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Current Sensors
Kirk Wallace wrote: These look pretty handy: http://www.pololu.com/catalog/product/1187 These look quite nice, the price is amazing! They should be fairly fast to respond. Jon -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Current Sensors
On Sun, 18 Mar 2012, Jon Elson wrote: Date: Sun, 18 Mar 2012 15:41:54 -0500 From: Jon Elson el...@pico-systems.com Reply-To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net To: Enhanced Machine Controller (EMC) emc-users@lists.sourceforge.net Subject: Re: [Emc-users] Current Sensors Kirk Wallace wrote: These look pretty handy: http://www.pololu.com/catalog/product/1187 These look quite nice, the price is amazing! They should be fairly fast to respond. Jon We use these in our 8I20, They work quite well (the chips are 3 dollarish) Note that 2100V isolation is marginal/not legal for 230V line operated equipment. -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your ()_() signature to help him gain world domination. -- This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
