True Bypass with NE555 Flip-Flop

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True Bypass with NE555 Flip-Flop

Postby AAntonio » 19 Apr 2016, 12:53

Hi
I have this scheme, for true bypass switch with very fast change
can someone help me with the pcb? I do not know.

https://www.youtube.com/watch?v=w8rSx8CIKIM
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Re: True Bypass with NE555 Flip-Flop

Postby mictester » 19 Apr 2016, 14:34

I hope that you don't expect to power this from a battery!
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Re: True Bypass with NE555 Flip-Flop

Postby AAntonio » 19 Apr 2016, 14:41

mictester wrote:I hope that you don't expect to power this from a battery!



the pedals, go with power supply
but could you help me with the pcb?
consumes much for a battery?
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Re: True Bypass with NE555 Flip-Flop

Postby DarkRain » 19 Apr 2016, 21:16

This system was not tested with a battery. If you are using a small low power relay a battery could be used. When i design it / test it i was not thinking of that because all my pedals designs are not using batteries.

Regards,
DeX

PS: this system was made as an alternative to a uControler system that uses a relay - a little bit cheaper and also easier to implemet as you will not need a programmer, a microcontroler etc.
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Re: True Bypass with NE555 Flip-Flop

Postby mictester » 19 Apr 2016, 23:39

http://www.freestompboxes.org/viewtopic.php?f=13&t=13295 shows how to use a cheap bistable relay for "true" bypass. If you use the specified relay (easily available), the circuit only draws current during "setting" the relay. When switched to bypass, the capacitor in series with the relay coil provides the power to reset the relay. If you read through the thread, you'll see that people have expanded on the original idea, and added momentary switches and indicators. It's easy to add extra switched contacts - just add another relay in parallel!

Incidentally, the 555 will probably take more current than the whole of the rest of the circuit!
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Re: True Bypass with NE555 Flip-Flop

Postby Gabe_ » 15 May 2018, 17:44

I've deepen this NE555 true bypass thing, here's a few results I got, with schematics and PCBs.

PRO:
What's great is that you need very few small components to make it work. With a SMD NE555 and an Omron G6K-2P 9v relay, I've made it on a 2cm x 2.5cm PCB.
When you've found the right RC values for your relay (Mine are for an omron G6K-2P 9V), it works perfectly.

CON:
Consumption is high: 28mA when bypassed, 41mA when not bypassed and with a 2k resistance on the led. This would suck a 9V battery in 5 to 10 hours. This is no big deal with a power supply, unless your pedal is already consuming a lot, some power supplies being designed for 100mA max output, you might wanna be careful.
You need to match R1 and C1 (see my schematic) values to your relay's coil resistance. Otherwise you'll get false triggers/no trigging/fast successive on/off trigging while pushing the switch or keeping the switch pushed may bypass back the pedal after a few seconds.
A NE555 can feed up to 200mA. If the coil's resistance is too low, you may blow it.

A few pics and then the documents.
Image
Image
Image

Bypass_schematic.pdf

Bypass_PCB.pdf


Hope this will help!
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Re: True Bypass with NE555 Flip-Flop

Postby Zokk » 25 May 2018, 09:02

Hi

could you improve the current consumption if you change the NE555 to its CMOS equivalent for example a TS555?
In many applications, the CMOS version will perform the same way but with much less current consumption.
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Re: True Bypass with NE555 Flip-Flop

Postby Gabe_ » 26 May 2018, 10:24

Zokk wrote:Hi

could you improve the current consumption if you change the NE555 to its CMOS equivalent for example a TS555?
In many applications, the CMOS version will perform the same way but with much less current consumption.


I haven't tried but it should work. Even though LMC555 or ICM7555 max current output (100mA) is half of the 555, so one should be even more careful with the relay's choice.
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