Electronics-Lab.com Community

# heathtech

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1. ## pressure sensor.

I had wondered about this myself :P. I had assumed it was probably RF, but I had also considere doing a similar thing (in a much slower moving rotation) with brushes kind of like the brushes in a motor.
2. ## Beginning Projects

Well, ordering from the internet is probably your best bet. Google Digikey, Newark, or Mouser Electronics. But, if you live in or near a metropolitan area, I'm sure you can look in the phone book yellow pages and with some luck, you might find an industrial electronics supplier or something. In Louisiana where I live I have several, but they are local stores.

All inductors have coils, by definition.
4. ## Pressure tranducer Circuit help!!

I'm not exactly sure what you need here, please go into more detail. As far as a wheatstone bridge goes, I can help you with that. Do you know what a strain gauge is? It is a pressure transducer that varies resistance in a linear fashion when pressure is applied, and can be installed on one side of a Wheatsone Bridge. Do you understand the function of a Wheatstone bridge? Do you need a tutorial on that? Please tell me what you understand and I can help you.

6. ## Beginning Projects

It depends on how complicated you want your first circuit to be. Google for Variable regulated power supply schematics. I don't know how much you know by way of electronics theory, laws, etc. Tell us what you know about electronics and then someone can advise you. If your knowledge is small, I would start out with 9 volt batteries and some simple series/parallel resistor circuit arrangements, study the formulas for both, and measure the voltages across them with a voltmeter, which is a necessary piece of test equipment, and compare the formulas to the actual results. If you don't already have one, you can pick a cheap one up for around ten bucks. Again, expand on what you know in your next post!
7. ## R-S flip flop

Well, flip flops are bistable multivibrators. An input trigger causes the two outputs to "flip-flop" states. The ouputs are usually labeled Q and /Q (not Q). There are two transistors inside the flip-flop arranged symetrically. The input trigger is applied to both at the same time, but due to very slight imbalances in the circuits, one will conduct first, making one output go low , and feeding back a signal to the base of the other transistor, which turns it off, in turn causing the other output to go high. I think I'm explaining that correctly. Even when the triggering pulse is removed, the circuit "latches" itself in that state, until another triggering pulse comes along and "flip-flops" the circuit again. This, in effect, becomes a storage for one bit of information.
8. ## Soldering Help

The Weller model#WES51 iron that I use is ESD safe. It is reasonably priced but not cheap, and I use it all the time with no ESD issues.
9. ## Most interesting electronics-area?

feedback and control circuits and systems.
10. ## conversion from miliohms to voltage circuits

Are you referring to 100 ohm platinum RTD temperature probes when you mention Pt100? If, so, what is the project? I know a few things about temperature control circuits and might be able to help.
11. ## A timer question

I have an idea for the 555 timer that might work. Please someone correct me if this is wrong. I don't want to post a mistake, but I wanted to figure it out and have someone correct me if I'm wrong:
12. ## Limitation of current !!

My guess is that you are driving the amplifier too hard, causing overmodulation. There is no amplifier with infinite gain, so if your signal is driving too hard, the peaks of the signal get chopped and cause distortion.
13. ## HELP 4+0 Link intercom circuit analysis

I think everyone would tell you to be more specific and not to double post the same topic. At least provide some details.
14. ## Can I ask this?

Kids these days like to wire up all kinds of stuff on their automobiles (neon lights, stereo amps, crossovers) ...Maybe you can teach them how to do it without frying everything!
15. ## h-bridge dc motor control circuit Reworked

Hey folks After several suggestions from other folks (2 guys named Len and L. Chung) on the net I have a new finished schematic to post. I tried putting caps on the motor, but that didn't do the trick. As you can see by the new schematic, I added a schmitt trigger and some caps on the board. The circuit is no longer skipping the hole intermittently. However, as Murphey would have it, a new, much smaller problem is occuring. When the circuit is first energizes, the motor oscillates quickly back and forth irrespective of the optical switch. After a minute give or take, everything lines out and it acts correctly. This problem is less troublesome, because I put a switch on the motor lead, and as long as I don't unplug the power supply, I can turn the motor on via the switch and it picks up where it left off. I suspect that the problem lies in the charge/discharge cycles of the caps somewhere. Maybe someone might see something I don't see. Thanks
16. ## Analytical Instrumentation

Evidently I posted this in the wrong discussion thread. I apologize to the administrators if the topic was inappropriate for the forum I posted it in.
17. ## Analytical Instrumentation

Hey folks I'd like to know if there are any other members in this forum who work in my field. I am an instrument/analyzer technician for a petrochemical company. My work involves repairing electronic instruments in a lab environment (i.e. Gas chromatographs, mass spectrometers, uv, x-rays, and other forms of lab instruments) I would like to use this forum as a means of sharing and gaining knowledge!
18. ## h-bridge dc motor control circuit Reworked

Ok, thanks for all the posts and suggestions. I have taken all the comments from this forum and others and reworked my proto. It is working brilliantly (no skips on the encoder) I still have some minor quirks to fix, but, it is 99% working. I am going to revise the schematic to reflect all the changes and post it when I am finished. thanks.
19. ## h-bridge dc motor control circuit Reworked

The motor is very small. I don't think it pulls many amps. The H-bridge IC is not getting very hot at all. It is a gearmotor, and is only turning at 1/3 rpm /second. I think it is dissipating the heat OK. I'll add a heatsink if this becomes a problem. Can you show me schematically how you might filter the motor? There is something definately going on with the motor, because when I remove it from the circuit and put a voltmeter on the H_bridge outputs, The entire circuit operates 100% correctly. It is only when the motor load is connected that it fails.
20. ## h-bridge dc motor control circuit Reworked

i am going to try to post a schematic
21. ## h-bridge dc motor control circuit Reworked

I am going to try adding the second power supply and testing the circuit. I know for a fact that when the leads to the motor are disconnected and the logic circuitry is allowed to work without a load (i.e. I interrupt the optical sensor with a piece of paper and read the voltage at the h-bridge output.), the circuit works 100% the way it is supposed to. I am certain that noise from the brushes is the culprit. I did add the schmitt trigger between the sensor and the flip-flop CP input, but it had minimal effect. I do need to filter the motor back emf, but I do not have any caps at my disposal in the nanofarad range. To be frank, I am not an engineer. I am a repair tech who is helping to design a prototype lab instrument. Can a cap in the microfarad range work? I have plenty of those.
22. ## h-bridge dc motor control circuit Reworked

The switch from forward to reverse is intantaneous. There is no pause or delay between polarity changes. Another tech suggested that I condition my sensor signal with a scmitt trigger. He said the edge triggered flip flop might be sensitive to unclean input signals. What do you think? Any suggestions on the type of device and how to configure it?
23. ## h-bridge dc motor control circuit Reworked

Thanks Ante, The encoder is LED with an amplifier output. I need to do some modifications to the schematic, I'll try to post it later. However, I have turned off the room lights and encounter the same problem. Secondly, the motor is a gearmotor, i.e. the shaft turns at only 1/3 rev/ second. One additional note, the logic section works 100% when the motor is disconnected. I believe there might be intermittent back emf or something, but I am not sure the best way to filter it, if indeed this is it. My motor is constantly changing polarity/direction. When I put a capacitor across the motor leads it doesn't seem to help. Like I said before, I'm not a design engineer. This is a 24v brush motor being driven by 15 vdc (gives me desired speed/torque). The polarity changes at each 360 revolution of the shaft. I am using an LB1640 H-bridge IC to drive the motor. Any suggestions as to the best way to filter the noise?
24. ## h-bridge dc motor control circuit Reworked

I am designing a simple dc motor control circuit using a single 4013 cmos edge triggered d-style flip flop with the q-bar output fed back to the data input. The set and reset inputs are at ground potential. The clock pulse input is being used to toggle the outputs of the flip flop. Each high input changes the flip-flop output state. This is driving an H-bridge which in turn is driving a dc gearmotor. My problem is that intermittently, the optic sensor I am using is passing the "hole" on my encoder without changing the polarity to my motor. This is quite infrequent but is causing problems. I am not an experienced engineer, rather, a repair technician. I am just trying to prototype a more complex instrument and this is just part of the overall design. Does anyone have experience with this?
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