[1291] True Bypass Relay Test

Date: August 20th, 2012 | Comments : [6] | Categories: DIY.

Bypass Relay test

I configured this breadboard setup to run a life cycle test of the true bypass relay system that I sell. Over 100,000 cycles per board without a glitch!

I used an Arduino with a Proto Shield, to which I had mounted a small red breadboard. On the breadboard I placed a pair of transistors to provide the switch signal to the two bypass boards that were being tested. Also, a blue LED was added to indicate that the test was in progress.

The bypass boards are jumpered to a separate breadboard, which has a pair of LEDS for each to indicate status.

I then wrote a simple program for the Arduino to pulse the switch wire of each bypass board once per second for 100,000 cycles. The bypass relays toggle and the LEDs change status when the signal from the Arduino is detected. This made it easy to watch the breadboard and see the relay boards switching in unison. At any point if a relay had missed a switch cycle, the LED pairs would have been out of sync and the condition easily seen.

I would enter the lab and check the progress every hour by watching the LEDs pulsing once per second. If you get close to the pc boards, you can also hear the tiny click that the relays make when they switch. The top LEDs on each side are actually wired through their relays to verify that they are making contact.

After 100,000 cycles, the relay bypass boards had performed flawlessly. They never got out of sync, which indicates that no switch cycles were missed. Nor did I see anything but consistent pulsing of the LEDs.

You may have noted that the relays on the bypass boards are different colors. This is because they are parts from different manufacturers. The dark blue relay on the left board is a Panasonic and the white relay on the right bypass pcb is a Fujitsu dpdt. The AMZ micro-controlled bypass has been tested with 5 different manufacturer’s relays and performs well with all of them.

I am satisfied that the system is reliable and functions consistently as designed. If you hit the switch of a pedal 20 times per show, and played 365 shows per year, the 100,000 cycles is the equivalent of more that 13.7 years of pedal use.


6 Responses to “True Bypass Relay Test”

[3084] Nathan Says: 11:35 pm, September 2nd, 2012

Hi, is it possible to use a logic high/logic low signal to control your relay bypass boards- i.e. for a DIY Micro-controlled programmable fx switcher? Or is the current board only suitable for direct control w/ momentary switch?

[3086] admin Says: 6:35 am, September 3rd, 2012


Yes, in this test I am using a 5v logic output from the Arduino to control the bypass relay boards. The Arduino is driving a 2N5088 transistor (open collector) which is then jumpered to the switch wire on the bypass pcb.

When the Arduino pin goes high ( 5v), the transistor turns on and pulls the switch wire low (ground) and that toggles the relay.

You can probably drive it directly from the Arduino digital logic output (without the transistor), but that is not the setup that I used in this test.

regards, Jack

[3630] Franky47 Says: 1:45 pm, November 25th, 2012

Nice job!

Did you measure the quality of switching after the 100000 cycles? Like bleeding, clicking, maybe a change in the resistance (due to the contacts wearing off)?



[3634] admin Says: 9:26 am, November 26th, 2012

The Panasonic datasheet for the TQ2 relay says that its mechanical lifetime is a minimum of 100,000,000 cycles, and its minimum electrical lifetime is 200,000 cycles with a 30v/1A load. Guitar FX signals are much lower than 30v and 1A, so the lifespan would be even longer. Note that this minimum electrical spec is with the relay being cycled 20 times per minute, and we don’t stomp our foot pedals that often, which would also increase lifespan.

I did not measure the contacts after the tests, but I did install one of those boards in the SSM2166 prototype pedal and it is in operation on my pedal board with no problems.

I have the other test board and I could do some measurements on it but since I did not test it before running the cycles, I can only compare it against the datasheet specs.

[3635] Franky47 Says: 2:30 pm, November 27th, 2012

Thanks for the precisions.

Did you notice any clics/pops in the signal when the relay is actuated?

When using the classic true bypass wiring with a simple wire as the “effect” (only to measure the action of the relay), I can measure clics even with a grounded input.

[3637] admin Says: 12:55 pm, November 28th, 2012

No clicks or pops in my applications, but just like the classic 3PDT, it will depend on what is connected to the switch (or relay). The dc bias from the pedal or external circuit is what is causing the pop, not the 3PDT or the relay.

You may be measuring switch contact bounce with the 3PDT footswitches, and the bounces may or may not be audible. Relay contacts typically have less mass, and therefore less bounce than a heavy manual switch.

regards, Jack


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