Re: slightly OT, need some electronic circuit help
On Sun, Oct 7, 2012 at 8:52 PM, Michael Torrie torr...@gmail.com wrote: On 10/07/2012 08:39 PM, Ryan Byrd wrote: I have only one power supply. It's called a battery. I cannot add a second battery. This is on a vehicle. well... you could get a dc-dc converter that takes 12v in and outputs 24v, like this http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_155695_-1 then, with 24v you could use a pair of resistors in a voltage divider circuit to get +/- 12v: http://en.wikipedia.org/wiki/Voltage_divider That may work... though the current rating is rather low. Another option is to use an 12-120v inverter and then use a computer power supply. ATX, for example, has +/- 12 volt outputs: http://jwenet.net/notebook/2005/1161.html Hmm, sounds complicated. Will give it some thought. There is an app on iPhone and Android called iCircuit for building and simulating circuits. I believe the iPhone app is more feature rich as it was just barely released for Android. Cheers, Stephen /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
On 10/07/2012 08:52 PM, Michael Torrie wrote: Another option is to use an 12-120v inverter and then use a computer power supply. ATX, for example, has +/- 12 volt outputs: http://jwenet.net/notebook/2005/1161.html Hmm, sounds complicated. Will give it some thought. Actually there are DC-DC computer power supplies available that supply +/- 12V, +/- 5V. However these, and indeed all computer power supplies, are switching power supplies and they need a load to even come on. So they won't really work for my needs. I've used computer power supplies before for other purposes, and I had to put a big resister across one of the 12V lines to load it enough to even come on. Ironically, about 10 minutes of coding on an Arduino could control an actuator quite easily, with a switch and a couple of relays. But try as I might I cannot get good info on doing what, a couple of decades ago, was common place electronics. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
Perhaps I don't fully understand the problem, but couldn't you use an H-bridge to control the motor (only needing 1 DC power supply) and an ADC on the Arduino to measure the position? The code in the Arduino would provide the basic feedback loop allowing you to set rough ADC values from the pot for your 3 positions. -Hugh On Mon, Oct 8, 2012 at 9:38 AM, Michael Torrie torr...@gmail.com wrote: On 10/07/2012 08:52 PM, Michael Torrie wrote: Another option is to use an 12-120v inverter and then use a computer power supply. ATX, for example, has +/- 12 volt outputs: http://jwenet.net/notebook/2005/1161.html Hmm, sounds complicated. Will give it some thought. Actually there are DC-DC computer power supplies available that supply +/- 12V, +/- 5V. However these, and indeed all computer power supplies, are switching power supplies and they need a load to even come on. So they won't really work for my needs. I've used computer power supplies before for other purposes, and I had to put a big resister across one of the 12V lines to load it enough to even come on. Ironically, about 10 minutes of coding on an Arduino could control an actuator quite easily, with a switch and a couple of relays. But try as I might I cannot get good info on doing what, a couple of decades ago, was common place electronics. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */ -- _ www.i-su-root.com /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
On 10/08/2012 11:36 AM, Hugh Clark wrote: Perhaps I don't fully understand the problem, but couldn't you use an H-bridge to control the motor (only needing 1 DC power supply) and an ADC on the Arduino to measure the position? The code in the Arduino would provide the basic feedback loop allowing you to set rough ADC values from the pot for your 3 positions. Of course. I said all that before[1]. Digital circuits are nice, but nothing beats the reliability of a simple analog circuit. I found some good info on op-amps, how they work, unipolar circuits, and exactly what the different resistance values give you. My application is in a very rough environment (dirt, dust, vibration, and extreme temperatures). The simpler the circuit the better. Arduino is way overkill for this application. All in all, this is a case study in why we computer people could probably use a bit of electronics (analog as well as digital) knowledge rather than falling back to code, though that does work very well in many cases. And if I was making a robot I would do it in code, and not use an analog circuit. [1] I've noticed a strong correlation between top-posting and not reading the e-mail one is responding too! You missed the last paragraph of my last e-mail. Posting inline with the quotes helps eliminate this problem. Just saying... /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
I've noticed a strong correlation between bottom posting and judging others for not bottom posting. Top posting helps eliminate this problem. Just saying... ;) --j On Mon, Oct 8, 2012 at 10:57 AM, Michael Torrie torr...@gmail.com wrote: [1] I've noticed a strong correlation between top-posting and not reading the e-mail one is responding too! You missed the last paragraph of my last e-mail. Posting inline with the quotes helps eliminate this problem. Just saying... /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
On 10/08/2012 12:30 PM, justin wrote: I've noticed a strong correlation between bottom posting and judging others for not bottom posting. Top posting helps eliminate this problem. Just saying... ;) Ahh the memories. Good times. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: definitely OT now :)
On 10/08/2012 12:46 PM, Michael Torrie wrote: On 10/08/2012 12:30 PM, justin wrote: I've noticed a strong correlation between bottom posting and judging others for not bottom posting. Top posting helps eliminate this problem. Just saying... ;) Ahh the memories. Good times. And I can't resist pointing out you haven't actually disputed my argument or observation. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: definitely OT now :)
I think the prospect of a Canadian winter has Michael feeling feisty. On Monday October 8 2012 12:53:17 Michael Torrie torr...@gmail.com wrote: On 10/08/2012 12:46 PM, Michael Torrie wrote: On 10/08/2012 12:30 PM, justin wrote: I've noticed a strong correlation between bottom posting and judging others for not bottom posting. Top posting helps eliminate this problem. Just saying... ;) Ahh the memories. Good times. And I can't resist pointing out you haven't actually disputed my argument or observation. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
On 10/08/2012 11:57 AM, Michael Torrie wrote: On 10/08/2012 11:36 AM, Hugh Clark wrote: Perhaps I don't fully understand the problem, but couldn't you use an H-bridge to control the motor (only needing 1 DC power supply) and an ADC on the Arduino to measure the position? The code in the Arduino would provide the basic feedback loop allowing you to set rough ADC values from the pot for your 3 positions. Of course. I said all that before[1]. Digital circuits are nice, but nothing beats the reliability of a simple analog circuit. I found some good info on op-amps, how they work, unipolar circuits, and exactly what the different resistance values give you. My application is in a very rough environment (dirt, dust, vibration, and extreme temperatures). The simpler the circuit the better. Arduino is way overkill for this application. The large current requirement (10A) and the need for a middle position make the circuit interesting and difficult to achieve using low cost analog components. An analog H bridge would work well if you only needed 2 positions. You can't dump that much current through an ordinary op amp. (Audio amplifiers use big, expensive op amps that easily surpass the cost of an Arduino.) PWM is the usual solution for handling that much current. However, can you achieve the middle position using a simple mechanical spring? That would allow you to use a very simple H bridge. It would help a lot to understand the application better. What kind of resting position do you want? When the power is lost, do you want it to revert somewhere, or hold its position firmly/loosely? Shane /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
Why not just use a mechanical switch at each position, put some capacitance in the input circuit for hysteresis/debouncing, and use relays to control direction? /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
On 10/08/2012 01:30 PM, Shane Hathaway wrote: The large current requirement (10A) and the need for a middle position make the circuit interesting and difficult to achieve using low cost analog components. An analog H bridge would work well if you only needed 2 positions. You can't dump that much current through an ordinary op amp. (Audio amplifiers use big, expensive op amps that easily surpass the cost of an Arduino.) PWM is the usual solution for handling that much current. However, can you achieve the middle position using a simple mechanical spring? That would allow you to use a very simple H bridge. It would help a lot to understand the application better. What kind of resting position do you want? When the power is lost, do you want it to revert somewhere, or hold its position firmly/loosely? Okay, so here's what I have. I have a linear actuator, which is essentially a screw driven by a motor. And the actuator has a built-in potentiometer to give you position. The motor uses very little or lots of amps depending on the load. I won't be having much load, so the amp draw is very low, like under 1 amp at 12 VDC, most likely. The actuator, being a screw, cannot move when power is not on. So I don't need to hold it actively. It is also very slow (compared to a servo), so PWM is not required. Full on voltage or no voltage is sufficient. As I said before, I don't need super-accurate positioning, so I don't need the actuator to seek back and forth around the target point. When it gets there it can just stop, even if it's too far or too close by a small amount. This actuator is controlling a hydraulic valve assembly so it only needs three positions: extended, middle, and retracted. It will always be in one of these positions; there's no resting position. Nick's idea of using limit switches is a good idea. I am confident a simple circuit can do it all without that kind of extra mechanical stuff though. Really I'm not worried about amp draw because I can use the result of the op amps to drive a relay to switch the higher amps if I need to. /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
On 10/08/2012 02:03 PM, Michael Torrie wrote: On 10/08/2012 01:30 PM, Shane Hathaway wrote: The large current requirement (10A) and the need for a middle position make the circuit interesting and difficult to achieve using low cost analog components. An analog H bridge would work well if you only needed 2 positions. You can't dump that much current through an ordinary op amp. (Audio amplifiers use big, expensive op amps that easily surpass the cost of an Arduino.) PWM is the usual solution for handling that much current. However, can you achieve the middle position using a simple mechanical spring? That would allow you to use a very simple H bridge. It would help a lot to understand the application better. What kind of resting position do you want? When the power is lost, do you want it to revert somewhere, or hold its position firmly/loosely? Okay, so here's what I have. I have a linear actuator, which is essentially a screw driven by a motor. And the actuator has a built-in potentiometer to give you position. The motor uses very little or lots of amps depending on the load. I won't be having much load, so the amp draw is very low, like under 1 amp at 12 VDC, most likely. The actuator, being a screw, cannot move when power is not on. So I don't need to hold it actively. It is also very slow (compared to a servo), so PWM is not required. Full on voltage or no voltage is sufficient. As I said before, I don't need super-accurate positioning, so I don't need the actuator to seek back and forth around the target point. When it gets there it can just stop, even if it's too far or too close by a small amount. This actuator is controlling a hydraulic valve assembly so it only needs three positions: extended, middle, and retracted. It will always be in one of these positions; there's no resting position. Nick's idea of using limit switches is a good idea. I am confident a simple circuit can do it all without that kind of extra mechanical stuff though. Really I'm not worried about amp draw because I can use the result of the op amps to drive a relay to switch the higher amps if I need to. Ok, it seems like you want 2 op-amps wired as comparators. One op amp decides whether to move the motor forward, the other decides whether to move it backward. (You can get multiple op-amps on a chip, so this doesn't increase the parts count.) You'll have to calibrate the circuit so that the op amps don't activate simultaneously. To keep things simple, let's say each op amp drives a DPST (or DPDT) relay. That solves your voltage issue: it isolates the control circuit from the motors, so you can apply reverse voltage to the motors. You can also use a voltage regulator in case the supply is too noisy. Each op amp should perform a slightly different comparison. When you want the middle position, the op amp that controls forward movement should compare the motor sense voltage with a voltage slightly lower than the control voltage, while the other op amp compares the motor sense voltage with a voltage slightly higher than the control voltage. You can adjust the voltages using resistor-based voltage dividers. Does that make sense? The comparator circuit on this page is a good reference: http://www.swarthmore.edu/NatSci/echeeve1/Class/e72/E72L2/Lab2%28OpAmp%29.html Shane /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Re: slightly OT, need some electronic circuit help
On 10/08/2012 03:18 PM, Shane Hathaway wrote: Ok, it seems like you want 2 op-amps wired as comparators. One op amp decides whether to move the motor forward, the other decides whether to move it backward. (You can get multiple op-amps on a chip, so this doesn't increase the parts count.) You'll have to calibrate the circuit so that the op amps don't activate simultaneously. To keep things simple, let's say each op amp drives a DPST (or DPDT) relay. That solves your voltage issue: it isolates the control circuit from the motors, so you can apply reverse voltage to the motors. You can also use a voltage regulator in case the supply is too noisy. Good to know I'm on the right track. I was thinking along these very lines in fact just when I noticed your e-mail. Each op amp should perform a slightly different comparison. When you want the middle position, the op amp that controls forward movement should compare the motor sense voltage with a voltage slightly lower than the control voltage, while the other op amp compares the motor sense voltage with a voltage slightly higher than the control voltage. You can adjust the voltages using resistor-based voltage dividers. Does that make sense? The comparator circuit on this page is a good reference: http://www.swarthmore.edu/NatSci/echeeve1/Class/e72/E72L2/Lab2%28OpAmp%29.html Absolutely makes sense! This is the track I'm heading down. Thank you very much for your thoughts on this. I knew there had to be a relatively easy way of accomplishing this. Michael /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
Meeting this Wednesday at 7:30pm -- FreeSWITCH
Date: Wednesday, October 10th, 2012 Time: 7:30 PM Location: C7 Data Centers (Lindon) Tod Hansmann will be presenting on FreeSWITCH. The goal is a small office setup. We will be going over the following, as this is very intro level, and FreeSWITCH is incredibly vast: - FS architecture - A brief, almost useless intro to SIP - Getting and compiling FS (quick overview) - Some typical module explanations and configurations - The default dialplan (including some IVR stuff) - Connecting phones to it - Gateways (or How I connect it to other people's phones) - Where to go from there More info: http://plug.org/pipermail/plug/2012-September/028779.html We will be meeting at the C7 facility at Canopy Building 5 in Lindon, behind Home Depot. You will need to bring a photo ID in order to sign in at the front desk. http://plug.org/c7dc http://www.plug.org/node/189 /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
