electronics question
-
NOT ELECTRONICS ENOUGH!!!
"Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!" — Hunter S. Thompson
-
FET transistors can replace relays in a dc circuit by properly biasing them. I haven't kept up with current parts, but even 20 years ago they were handling 100A loads. I'm sure they can do better today. The nice thing about FETs is that the gate terminal draws near zero current, so it's easy to set switching thresholds using a simple resistor divider. I can't look too closely at the circuit right now, as my employer actually expects me to work on job related stuff while I'm here, but I'll take another look tonight.
Will Rogers never met me.
Thanks Roger, I am looking into FET transistors right now. Looks promising, but so far I am not sure how to make them work.
Roger Wright wrote:
as my employer actually expects me to work on job related stuff while I'm here
Dang bosses can be so unreasonable some times, sure glad I do not have one (unless you count the wife :~ )
Roger Wright wrote:
I'll take another look tonight
Thanks
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
-
wizardzz wrote:
NOT ELECTRONICS ENOUGH!!!
I am so sorry. Can you recommend something much more complicated that will do the same job?
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
1/6 7404
-
I defer to you, o great one, but would you recommend an SCR for high loads instead? Or are those only for AC? /ravi
My new year resolution: 2048 x 1536 Home | Articles | My .NET bits | Freeware ravib(at)ravib(dot)com
An SCR relies on a zero-crossing to shut off, so it is best used for ac loads.
Will Rogers never met me.
-
An SCR relies on a zero-crossing to shut off, so it is best used for ac loads.
Will Rogers never met me.
Right! I remember building (not designing) a circuit that used SCRs to control 60W bulbs to flash in time with an audio signal. /ravi
My new year resolution: 2048 x 1536 Home | Articles | My .NET bits | Freeware ravib(at)ravib(dot)com
-
Thanks Roger, I am looking into FET transistors right now. Looks promising, but so far I am not sure how to make them work.
Roger Wright wrote:
as my employer actually expects me to work on job related stuff while I'm here
Dang bosses can be so unreasonable some times, sure glad I do not have one (unless you count the wife :~ )
Roger Wright wrote:
I'll take another look tonight
Thanks
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
PJ Arends wrote:
unless you count the wife :~
Having a wife counts as having two bosses - her whims, and her hormones. ;P
Will Rogers never met me.
-
For those who are electronically inclined: http://www3.telus.net/pja/circuit.png[^] I was wondering if there was a way to replace the three internal relays with something else in order to make the circuit solid state. I know that a normally open relay can be replaced with a transistor, but what about a normally closed one? Is there a component that will break a circuit when power is applied to it? Similar to a transistor but with the opposite effect. Also, do I have my diodes in the correct direction? Does DC power flow from positive to negative or the othe other way around? Thanks
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
Check my logic before I continue, PJ. And yes, you can use a PNP transistor to break a circuit when the input is positive using a common-emitter configuration. Anyway... I've labelled the three relays as K1, K2, K3, from left to right. I've also designated S1, S2, and SL for obvious reasons. Convention is Kn TRUE when energized, Sn TRUE when closed. Looking over the circuit it seems the following can be said of it: K1 = S2 + K1*S1 + K2*K3*SL (the second term implies that K1 remains TRUE as long as S1 remains TRUE - a latch) K2 = S2 + K2*K3*SL K3 = K1*S1 The loads are energized when: L1 = (not K1)*S1 L2 = K2*K3 Is this what you intended? Or did I misread something? If so, describe what the circuit is supposed to do. If I've got it right, we can easily put together a solid state version of the control logic using cheap low-power transistors and diodes, and drive the output with power FETs (if they're also DC devices). In any case, this can be made simpler, and probably cheaper by going with silicon.
Will Rogers never met me.
-
For those who are electronically inclined: http://www3.telus.net/pja/circuit.png[^] I was wondering if there was a way to replace the three internal relays with something else in order to make the circuit solid state. I know that a normally open relay can be replaced with a transistor, but what about a normally closed one? Is there a component that will break a circuit when power is applied to it? Similar to a transistor but with the opposite effect. Also, do I have my diodes in the correct direction? Does DC power flow from positive to negative or the othe other way around? Thanks
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
-
Check my logic before I continue, PJ. And yes, you can use a PNP transistor to break a circuit when the input is positive using a common-emitter configuration. Anyway... I've labelled the three relays as K1, K2, K3, from left to right. I've also designated S1, S2, and SL for obvious reasons. Convention is Kn TRUE when energized, Sn TRUE when closed. Looking over the circuit it seems the following can be said of it: K1 = S2 + K1*S1 + K2*K3*SL (the second term implies that K1 remains TRUE as long as S1 remains TRUE - a latch) K2 = S2 + K2*K3*SL K3 = K1*S1 The loads are energized when: L1 = (not K1)*S1 L2 = K2*K3 Is this what you intended? Or did I misread something? If so, describe what the circuit is supposed to do. If I've got it right, we can easily put together a solid state version of the control logic using cheap low-power transistors and diodes, and drive the output with power FETs (if they're also DC devices). In any case, this can be made simpler, and probably cheaper by going with silicon.
Will Rogers never met me.
Roger, sorry it took me so long to respond, we were out late last night.
Roger Wright wrote:
describe what the circuit is supposed to do
Ok, the purpose of the circuit is to control the hydraulic system of a dump box. Load 1 would be the solenoid[^] that controls the pump that lifts the box. Load 2 would be the electric solenoid actuator[^] that drains the lift cylinder. Currently I have to stand by and hold the switch that lowers the box, and as it is simply a gravity system this can take a while, time that I could be using to do something else. What I want is to press and hold S1 to raise the box. then press and release S2 to start the box lowering. At any point while the box is lowering I want to be able to press S1 to stop it, without starting the pump to raise it. The circuit is what I came up with to do this. At the start of the cycle, all three switches are open; K1 and K2 are open; and K3 is closed(it is an NC relay) Press and hold S1 to raise the box Current runs through K1 to accuate L1 SL closes (goes to TRUE) as the box is lifted off it's trigger Release S1 when box is high enough Press S2 to lower the box Current flows through the coils of K1 and K2 setting both of them to TRUE Current flows through K3 and K2 to accuate L2 - box lowers Current also flows through SL to hold K1 and K2 closed, thus S1 can be released and current will still flow. At this point one of two things can happen: 1 - The box makes it all the way down This opens SL as the box settles on it's trigger SL opens, causing K1 and K2 to also open K2 opening causes L2 to open We are back at our original starting configuration 2 - I press S1 to stop the box from going down Because K1 is TRUE, Current flow will hold K1 where it is, and it will also accuate K3 K3 is open, breaking the current that holds K2 closed &nb
-
Solid state relays[^] come in both flavors, normally open and normally closed. What's that, BTW (if it isn't confidential)? A headache generator for electronics students? ;)
Thanks, that could be exactly what I am looking for :)
Indivara wrote:
What's that, BTW (if it isn't confidential)? A headache generator for electronics students?
See my reply to Roger above, and if this causes headaches for students they better look at a different career path.
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
-
Roger, sorry it took me so long to respond, we were out late last night.
Roger Wright wrote:
describe what the circuit is supposed to do
Ok, the purpose of the circuit is to control the hydraulic system of a dump box. Load 1 would be the solenoid[^] that controls the pump that lifts the box. Load 2 would be the electric solenoid actuator[^] that drains the lift cylinder. Currently I have to stand by and hold the switch that lowers the box, and as it is simply a gravity system this can take a while, time that I could be using to do something else. What I want is to press and hold S1 to raise the box. then press and release S2 to start the box lowering. At any point while the box is lowering I want to be able to press S1 to stop it, without starting the pump to raise it. The circuit is what I came up with to do this. At the start of the cycle, all three switches are open; K1 and K2 are open; and K3 is closed(it is an NC relay) Press and hold S1 to raise the box Current runs through K1 to accuate L1 SL closes (goes to TRUE) as the box is lifted off it's trigger Release S1 when box is high enough Press S2 to lower the box Current flows through the coils of K1 and K2 setting both of them to TRUE Current flows through K3 and K2 to accuate L2 - box lowers Current also flows through SL to hold K1 and K2 closed, thus S1 can be released and current will still flow. At this point one of two things can happen: 1 - The box makes it all the way down This opens SL as the box settles on it's trigger SL opens, causing K1 and K2 to also open K2 opening causes L2 to open We are back at our original starting configuration 2 - I press S1 to stop the box from going down Because K1 is TRUE, Current flow will hold K1 where it is, and it will also accuate K3 K3 is open, breaking the current that holds K2 closed &nb
I'm working on it, PJ. I've got a circuit laid out that I think will do the job, but getting it into a form to post will take a while. Besides, I need to look up a few part numbers for you, since they don't make the ones I've memorized anymore.
Will Rogers never met me.
-
I'm working on it, PJ. I've got a circuit laid out that I think will do the job, but getting it into a form to post will take a while. Besides, I need to look up a few part numbers for you, since they don't make the ones I've memorized anymore.
Will Rogers never met me.
That is great Roger, thanks. I am also learning quite a bit while researching this little project. It is actually quite fun and interesting. Look forward to seeing what you come up with.
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
-
That is great Roger, thanks. I am also learning quite a bit while researching this little project. It is actually quite fun and interesting. Look forward to seeing what you come up with.
You may be right I may be crazy -- Billy Joel -- Within you lies the power for good - Use it!
Check your email... answer enclosed, since I'm too dumb to figure out how to post it on my website.
Will Rogers never met me.
