Motor Control
Motor Control
(OP)
On an actuator i have an RVDT that provides a voltage of 0V at minimum stroke and 10V at maximum stroke. How do i use this voltage to shut off the 28V dc motor at either end of the stroke?? What should the circuit contain?
Please help! it'd be greatly appreciated.
Please help! it'd be greatly appreciated.





RE: Motor Control
RE: Motor Control
RE: Motor Control
Well, i'm considering using LVDT & RVDT's to replace current unreliable micro-switches.
I have an aerospace unit that currently has an RVDT attached onto it. I also have a signal conditioning chip that i am currently linking up on some veri-board. I can scale the output voltage how i want, which will probably end up as 5V at min stroke & 15V at max stroke. It is using these output DC voltages to cut the motor that is giving me grief.
RE: Motor Control
<nbucska@pcperipherals.com>
RE: Motor Control
If you do, then i have considered it and found they cannot operate at the altitudes & temperatures required.
RE: Motor Control
temp. Is there any other limitation or requirement
we need to know to answer your question?
<nbucska@pcperipherals.com>
RE: Motor Control
It's on a Hawk aircraft so altitude 25,000ft, temp from -60 to 125 degrees C.
RE: Motor Control
Someone must make mil.spec part...
<nbucska@pcperipherals.com>
RE: Motor Control
Someone must make mil.spec part...
You may try HALL-sensor, too. Optical one may get dirty...
<nbucska@pcperipherals.com>
RE: Motor Control
I have already settled on an RVDT and need a circuit that will take a voltage, compare it against a reference and disconnect the motor.
RE: Motor Control
sensitivity or positional accuracy.
<nbucska@pcperipherals.com>
RE: Motor Control
Can you quickly explain what a dual power dc supply is and what advantages it has over a single power supply?
Many thanks.
RE: Motor Control
Comparators could work depending on the accuracy. You can get a DC rated relay/contactor to handle the motor load (need more info on the 28VDC motor). This relay would be energized by the comparator circuit. There is lots of ways to do this that is just one way. Ill wait for more info.
RE: Motor Control
The dual supply is just that: one supply with two or more outputs usually with different voltages.
<nbucska@pcperipherals.com>
RE: Motor Control
The accuracy isn't gretaly important at the moment, just a generic circuit to compare an input voltage with the position voltage and disconnect motor.
RE: Motor Control
I need to know what to put in the black box to cut the motor at the 5 & 15V.
RE: Motor Control
The high or low output of the comparator would energize or de-energize the relay that is carrying the electrical load of the actuator.
Some links below (randomly selected-search google for comparator circuits) will help, some are very basic some are detailed.
http://www.maxim-ic.com/appnotes.cfm/appnote_number/886
http://www.allaboutcircuits.com/vol_6/chpt_6/2.html
http://home.cogeco.ca/~rpaisley4/Comparators.html
Pay close attention to the data sheet for operating temperature and altitude. A commercial grade part will not be adequate. Military spec parts are definately in order.
There are other methods that might work better such as a PLC with a analog to digital card or a microcontroller with the same AD card. These would take more time to develop (possibly) depending on if you have worked with either before.
One other note, the temp range your dealing with will cause the reference voltage to drift, how much depends on how much you want to spend. If the reference voltage drifts, say +-10% over the operating range (cheaper voltage reference) then this will directly affect where the actuator motor is stopped.
RE: Motor Control
- a digital output which will be easier to interface to than an RVDT
- simple power requirements
- no moving parts other than whatever they are detecting the position of
- are physically small and light
- capable of service in some pretty hostile environments.
They're popular in the chemical process and power generation industries because they are tough and reliable, plus they are simple - which suits us just fine! I think you may be making this unnecessarily complicated involving RVDTs.
-----------------------------------
Start each new day with a smile.
Get it over with.
RE: Motor Control
As for the proximity suggestion, i'm looking to replace the discreet micro-switches with a continuous system. This way, any later systems e.g auto pilot can interface with the output voltage.
RE: Motor Control
Based on your last post, you may want to use the analog-digital route as this will offer the most flexibility. However, the comparators can also offer this flexibility but without all the possible features of a microcontroller or PLC based system (interfacing to displays, having user adjustments, etc).
For the comparators, if you wanted it to stop in the middle, I assume the voltage would be 10V. This would require the reference voltage to be changed to 10V, which can be done. There are adjustable voltage regulators that would simply require a variable resistor to be moved to change the output voltage. Now how you going to move the variable resistor? Could use a digital pot (variable resistor) and control this through some other software/hardware. Just some more thoughts to get your wheels a spinning, good luck.