Beginners: please read this post and this post before posting to the forum.
0 Members and 1 Guest are viewing this topic.
I have a circuit that has a very low power output, but I don't know how to increase the output without burning any components.
Hi,Quote from: Hal_Emmerich on June 27, 2010, 04:03:30 PMI have a circuit that has a very low power output, but I don't know how to increase the output without burning any components.If you have the PWM circuit you need, just use a transistor or two.Tell us what you've got (and output voltage and current) and you can get the rest here.Else, as TrickyNekro mentioned, a 555 could be used (again with a current booster transistor), or like half a 4093. There's several ways to shave that goat.
The circuit I am using is kind of complex (it uses 4 nand gates)
, but I will try to get a diagram of it up soon.
For the 555 timer, I was thinking about using the circuit at the bottom of this webpage: http://www.dprg.org/tutorials/2005-11a/index.htmlCan you tell what the maximum output of this circuit might be?
[...] is it true that one end of the SMA wire at a 30-40V source, and the other attached to the MOSFET,
and a 6Kohm resistor and LED are there to help control the current flow?
And also, would I need to change the 5-12V or 30-40V sources if I was using an IRF510 instead (that's the only MOSFET I have at the moment)?The IRF510 has a much lower current handling, only 5.6A, its max. voltage is 100V, so no problem there. R_ds_on is a bit high, 0.54 Ohm, but most important, you need at least 7..8V to drive it properly.For testing with less than 5.6A it's OK (assuming you use the needed voltage, i.e. 7V absolute minimum, 12V if possible).I don't know your application, but 5.6A at 30V (40V) is a healthy 168W (224W) and that's quite a bit of heat for an SMA app.How did you arrive at the figure of 30..40V?(Basing this on numbers from Dynalloy)If you use a 0.203 mm diameter wire with the following data: 29.1 Ohm/m, 570.0 g pull force, ~660 mA for a contraction time of 1s ("safe" value).With 30V (40V), you need to use 1.5m (2m) to keep the current from going higher.The IRF510 is able to handle 8 such wires in parallelJust an example, your wire is probably different.Quote from: Hal_Emmerich on June 28, 2010, 10:53:46 AMThe voltage I need for my wires and the PWM timing I need keeps changing, Now I feel it in my bones that this is a top secret But if you could reveal just some metrics, like how thick a wire, how long, how hard does it need to pull (min/max) and such, it might be easier to find the best solution.Do you have the wire?If you do, do you have a datasheet on it?If the specs keeps changing, wouldn't a microcontroller be a better option, as it could automate the regulation?
The voltage I need for my wires and the PWM timing I need keeps changing,
I assumed I would need 30V to 40V because I am using 0.015 inch diameter wire from Dynalloy
I was planning on using maybe six wires maybe around 14-20 inches to pull the lower arm from wires connected at the upper arm (longer is probably better because I think that naturally means more contraction).
I don't know if I should use different wire.
I really don't have an exact picture of what I need to do to finish this arm. Every time I try to experiment, I start thinking I'm using wires that are too short, but I'm also nervous about handling high voltages from one source.I was thinking I could just use several sources that are 20 V or less, where each source is a PWM current through the wire so I can keep the arm bent by sending periodic pulses to the wires until I turn it off and the arm lowers when the wires cool (I hope that makes sense).
I really wanted to use less than ten 9 V batteries to power the whole arm,
but I don't know what I will ultimately need. I really appreciate all your help, especially since I'm building this thing with little help and no experience. Thanks again!
Hi, this is the type of (12V,7A) SLA battery I could find that would suit my project based on Soeren's advice: http://www.batterymart.com/p-12v-7ah-sealed-lead-acid-battery.html#pr-header-SLA__12V7__F1
I'm not sure how I would attach this battery directly to my six SMA wires. Do I need alligator clips to attach to the batter? Or can I just wrap some stripped 22 gauge wire around the terminals to make a direct connection to a conductive surface on the other end of the wire?
Would it be all right to attach the wire straight from the battery into a breadboard, or would it fry the breadboard?
then I can put 22 gauge wires into the back of the spade terminal
I'm trying to make everything fit on a small breadboard and then preferably fit inside the arm or attach to the outside.
Based on the assumption that you will use 13.5AQuote from: Hal_Emmerich on June 30, 2010, 02:15:06 PMthen I can put 22 gauge wires into the back of the spade terminal22 is way to small. 12 is probably better (Soeren can you confirm?)Quote from: Hal_Emmerich on June 30, 2010, 02:15:06 PMI'm trying to make everything fit on a small breadboard and then preferably fit inside the arm or attach to the outside.If you are talking about solderless breadboard, putting 13.5A through it is probably a bad idea.
So spade terminals similar to these
I attach to the terminals of the SLA battery, then I can put 22 gauge wires into the back of the spade terminal, and you suggest that I make a wire from the positive end of the battery connect to a fuse similar to this (making sure they can handle the right current),
and then I continue a wire from the fuse into a switch like this (again making sure it can handle the current through my particaluar circuit)
and then that continues to one end of the SMA wires?
Do you have any recommendations on fuses and switches I can use? I'm trying to make everything fit on a small breadboard and then preferably fit inside the arm or attach to the outside.
And what did you mean by isolating exposed wires? I'm sorry, I don't know any of these simple terms.
Would it be possible for you to maybe modify those schematics you gave me for the 555 timer PWM circuit to help me understand how to wire up everything? If you can't, of course I will understand. I will try to ask some people at school if I can, but you seem more experienced than most people I talk to at my school! Thank you again for all the help you've given me.
EDIT: Added the fact that the SLA positive terminal goes to the SMA wires, not the breadboard.
22 is way to small. 12 is probably better (Soeren can you confirm?)