I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem.
Low Power High Voltage Flip Flop
Started by ●January 30, 2023
Reply by ●January 30, 20232023-01-30
On Monday, January 30, 2023 at 8:16:01 PM UTC+11, rhor...@gmail.com wrote:> I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem.You should be able to build a J/K flip-flop with discrete transistors - there are N-channel and P-channel MOSFETs that can take that kind of voltage. The gate-oxide isn't that robust, so you might need level shifters to make the logic work. It won't have to be that fast, so the level shifters won't need a lot of current. Classic CMOS is good for logic rails up to about 18V, but if there a 25V version I haven't heard of it. -- Bill Sloman, Sydney
Reply by ●January 30, 20232023-01-30
On 30.1.2023 11.15, rhor...@gmail.com wrote:> I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem.You may need to build a debounce circuit for the switch, else the response may be erratic, as the F/F will count the parity of the contact bounces. -- -TV
Reply by ●January 30, 20232023-01-30
On Monday, January 30, 2023 at 4:16:01 AM UTC-5, rhor...@gmail.com wrote:> I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem.You may think you need that, but actually you don't. You can most likely replace your existing switch with one of the exact same form factor that serves the on/off function. It will be called a "latching" on/ off switch.
Reply by ●January 30, 20232023-01-30
On Monday, January 30, 2023 at 5:16:01 AM UTC-4, rhor...@gmail.com wrote:> I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem.There are a number of simple circuits using a pair of transistors, which will do what you need. They take advantage of charge being stored on a capacitor to change the state of the circuit with the same push button. A Google search turned up a number of possibilities. The FET based designs can be very low power when off, however, you will need to find FETs with gate to source voltage ratings to match your power source. I would look for at least 30V. https://www.google.com/search?client=firefox-b-1-d&q=push+button+on/off+circuit Here's a page with FET devices. The link is long, so you may need to patch it up from this post. http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/electronic-circuits/push-button-switch-turn-on/latching-toggle-power-switch Figure 3 has the basic circuit. Other variations add different features. Figure 9 works with higher power source voltages. If you don't have a low voltage regulator, you can use resistors to step down the output voltage. -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●January 30, 20232023-01-30
On 1/30/2023 4:15 AM, rhor...@gmail.com wrote:> I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem.Is a latching relay too simple a solution: <https://www.electronicdesign.com/technologies/analog/article/21806385/relaybased-onoff-flipflop-remembers-state-during-power-failure>
Reply by ●January 30, 20232023-01-30
On Mon, 30 Jan 2023 01:15:57 -0800 (PST), "rhor...@gmail.com" <rhorerles@gmail.com> wrote:>I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem.You may not want to use this https://www.dropbox.com/s/okjq1x7q0ftbfig/Momentary_Nfet.jpg?raw=1 but it's a fun circuit. A version with two fets would stay on/off forever.
Reply by ●January 31, 20232023-01-31
On Monday, January 30, 2023 at 3:43:30 AM UTC-6, bill.... wrote:> On Monday, January 30, 2023 at 8:16:01 PM UTC+11, rhor.. wrote: > > I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem. > You should be able to build a J/K flip-flop with discrete transistors - there are N-channel and P-channel MOSFETs that can take that kind of voltage. > > The gate-oxide isn't that robust, so you might need level shifters to make the logic work. It won't have to be that fast, so the level shifters won't need a lot of current. > > Classic CMOS is good for logic rails up to about 18V, but if there a 25V version I haven't heard of it. > > -- > Bill Sloman, SydneyYeah, that is my notion. I need some details.
Reply by ●January 31, 20232023-01-31
On Monday, January 30, 2023 at 5:51:07 AM UTC-6, Fred Bloggs wrote:> On Monday, January 30, 2023 at 4:16:01 AM UTC-5, rhor... wrote: > > I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem. > You may think you need that, but actually you don't. You can most likely replace your existing switch with one of the exact same form factor that serves the on/off function. It will be called a "latching" on/ off switch.I guess I failed to mention it is not a simple switch. It is a rotary encoder with a momentary push button. If there is a rotary encoder of roughly the same size (~ 25mm with a ~6mm shaft) with an on/off switch rather than a momentary switch, I would love to use it. The design uses an EC11 rotary encoder.
Reply by ●January 31, 20232023-01-31
On Tuesday, January 31, 2023 at 12:43:59 AM UTC-4, rhor...@gmail.com wrote:> On Monday, January 30, 2023 at 3:43:30 AM UTC-6, bill.... wrote: > > On Monday, January 30, 2023 at 8:16:01 PM UTC+11, rhor.. wrote: > > > I have a situation where I need to change a momentary switch to an on / off switch. This is ordinarily very easy using a JK Flip Flop, but there is a twist. The device runs on a 6S Lithium battery, so the voltage will vary from about 18V to 25V or so. In addition, I need the power control circuit to use very little current - on the order of 100 uA - when off. It can use much more power when on - 20 mA or so is no problem. > > You should be able to build a J/K flip-flop with discrete transistors - there are N-channel and P-channel MOSFETs that can take that kind of voltage. > > > > The gate-oxide isn't that robust, so you might need level shifters to make the logic work. It won't have to be that fast, so the level shifters won't need a lot of current. > > > > Classic CMOS is good for logic rails up to about 18V, but if there a 25V version I haven't heard of it. > > > > -- > > Bill Sloman, Sydney > Yeah, that is my notion. I need some details.What is your notion? 4000 series CMOS won't handle the battery voltages you are talking about. You would need to add two transistors and a voltage regulator to make a 4000 series part compatible with high side switching your 25V power rail. You can do the same job with just the two transistors, no regulator and no 4000 series CMOS. I provided links to some sample circuits. Maybe you could provide a bit more feedback of what you see here that you like and don't like, and why? Feedback would help a lot. -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
