Apparently, I'm a bit of an exception at my workplace: most of the engineers are hired directly to full-time, whereas I was hired through a recruitment firm (Aerotek) that they usually use mainly for the technicians (with the contract that I would be hired full-time after 6 months.)
I'm kind...
Thanks for the suggestions guys.
Keith, I am using a single supply and the h-bridge to turn the direction.
"If you are then just use one of the amps in the single supply for current magnitude and you already know the direction. If you are using two supplies put one in each read the one...
For my application, I desire continuous dc motor torque control - the command torque can go from -'ve to +'ve quickly.
I made a previous post here regarding bidirectional motor control - with some good suggestions- basically, I'm having a tough time measuring the load current in the h-bridge...
I haven't had a chance to go back and double check that circuit configuration, but I think I may have found a better solution.
The LD 18200 is an Hbridge with built in current sensing: it works by composing the bridge transistors with many cells, each with equal share of the load current, and...
I tried hooking up the opamp/dual resistor configuration of Fig. 4, but realized I couldn't because the 2 lower transistors on the bridge are tied together in hardware.
So, I hooked up the circuit in Fig 5, using 50 kohm resistors and a 741 op amp. All I get at the output voltage (which is...
Thanks for the help guys. I'm getting a quote on the LEM sensors, although the ACS750 seems to provide the same electric isolation function as the LEM (to me, unless I'm missing something.)
That AD639 uses the same opamp high-common mode rejection difference amplifier configuration suggested...
How would I deteremine what values of the capacitors in this configuration? The appnote says they are used to smooth the transition between one direction and the other.
I'm trying to do bidirectional dc motor current (torque) control using resistors as the current sensor.
I'm using a bidirectional pwm/bridge IC combo (see www.solutionscubed.com), and I've tried the sense resistor placed between the bottom of the bridge and ground. It works well for PWM...
I know this topic has maybe been beaten to death, but nevertheless:
I have a dc motor in the lab, with a ratio=30 gear assembly, and tachometer attached to the rotor shaft.
For my application, I'm using it for torque (current control), using a fixed field.
This motor is intended for...
A Torsion bar torque sensor is just a torsion bar, with a means of measuring the angles on each side of the bar. The "twist" of the bar is then measured:
Torque from torque sensor= K*( input angle - output angle )
where k is a known stiffness constant.
So you just need to measure the input...
This isn't exactly motors related, but thought you guys might have some insight.
I'm trying to run some experiments on fault tolerant control for a dc motor torque control system with a torque sensor used as input for the current (torque) loop. Basically, this is an electric power steering...
1) relative cost of temperature sensor on armature of brushed dc motor.
2) Is Ra always proportional to temperature /temperature rise (besides, for instance, varying , slightly with other factors, such as brush resistance variation during commutation, and slow brush resistance wear over time)...
A followup question/clarification:
I see the brush drop increases as motor speed/ armature current increase (from BobM3's post). I've seen some papers which model the brush (arc) drop as Vd=Const*Ia*Wm.
Many Electric machine books say the brush drop can be modeled as a voltage drop or...
skogsgurra,
From what I've read the resistance increases as the brush wears, but given your explanation it makes sense that the resistance would decrease. Hmmmn.
Sreid,
Just to verify: You are saying the brushes do change resistance over a longer period of time due to wear,
or that there...
