# Help solve this *simple* circuit riddle

#### namnguyen80

Joined May 19, 2020
12
This is for a scooter. I bought 2 new pieces, and both didn't work. Maybe it's something else. I checked the motor, all connections, pretty much everything else.

So here's the very simple 2 relays controller:

The two relays have identical label. The pins for 1st relay is 1,2,3,4,5, 6 and the 2nd relay is 12,13,14,15,16,17.

The relay is NC on pins 2 and 3. Pins 5 and 6 are control coil pins. 1 , 2 and 4 are always connected.

When power is applied to pin 7, pins 2 and 3 are connected, so power flows to 1, then 4 and 13. When the on switch is pressed (open), pins 2 and 3 are disconnected, and no power on pin 13.

It would need to have the 2nd relay closed, to have 13 flows to 15.

That's simple, but it doesn't work.

When thinking about functionality, the board supports an on off switch (20,21) and brake (18,19). It also detects low voltage and also if charger is connected.

The on/off switch is curiously normally closed. So when power is on, the relay 1 (pins 1,2,3,4,5,6) closes and power goes through to pin 13.
The second relay is for the brake. When press the brake, it opens up the brake switch.

So, can someone please explain to me what's going on, how it is designed to work, and why the power is not going to pin 15 (or 11)?

On the other side, there are two relays 1,2 and also the diode on pins 9 and 10.

#### KeithWalker

Joined Jul 10, 2017
2,925
That is NOT a simple problem, With the lack of a schematic diagram I don't have enough information to understand your question.

#### namnguyen80

Joined May 19, 2020
12
That is NOT a simple problem, With the lack of a schematic diagram I don't have enough information to understand your question.
I was hoping someone experienced with this would be able to zoom into the image and see what's going on.
But I hear you, it may not be a simple problem.

#### wayneh

Joined Sep 9, 2010
17,469
I'm with @KeithWalker. What makes you think this is simple?

#### wayneh

Joined Sep 9, 2010
17,469
I checked the motor, all connections, pretty much everything else.
How did you check the motor? Did you actually probe the connections for continuity, or just a visual inspection.

I'd look for the wiring diagram and a troubleshooting guide if you can find one. Then probe for voltages and check ground wires. I've seen wires fail by corroding inside the insulation after a slight damage. You cannot take anything for granted.

#### LesJones

Joined Jan 8, 2017
4,106
For anyone to be able to make sense of it you need to trace out the schematic of the wiring between the board and all the switches and controls and between the board and the motor. Also some background information would be helpful. Such as the nature of the failure of the original board and what made you conclude that board was the cause of the fault. Properly focused pictures of both sides of the board would also be helpful with labels showing where all the wires go to.

Les.

#### namnguyen80

Joined May 19, 2020
12
For anyone to be able to make sense of it you need to trace out the schematic of the wiring between the board and all the switches and controls and between the board and the motor. Also some background information would be helpful. Such as the nature of the failure of the original board and what made you conclude that board was the cause of the fault. Properly focused pictures of both sides of the board would also be helpful with labels showing where all the wires go to.

Les.
The other side only has 2 relays and the diode.

The motor works. I put a 12v voltage controller on it, and I was able to ride the scooter. This is the one that you can vary motor speed with a dial (potentiometer).

Along with that, the on/off switch also works, since it's part of the connection, and so is the fuse/reset component.
The charging plug was not connected, but the only issue I can see is that the + and - of it touches and causes a short. However, I checked that also and unplugged it before to see if it makes any difference.

So 2 things left, one is the throttle and the other is the brake. Both are 2 wires open/close circuit. I was wondering if it's variable resistor for the throttle. However, with the board having no heat sink and no power PWM, it's probably a simple 2 relays controlled by on/off circuit, not variable resistor (which usually use 3 wires).

#### namnguyen80

Joined May 19, 2020
12
How did you check the motor? Did you actually probe the connections for continuity, or just a visual inspection.

I'd look for the wiring diagram and a troubleshooting guide if you can find one. Then probe for voltages and check ground wires. I've seen wires fail by corroding inside the insulation after a slight damage. You cannot take anything for granted.
The wirings are very clean and new. I did check for loose wires.

#### namnguyen80

Joined May 19, 2020
12
I'm with @KeithWalker. What makes you think this is simple?
Well, who know what the experienced people can do, and I maybe wrong on that.

In addition, here's how I think it's simple. Just based on what a designer would do for the requirements of this controller, taken cheap design in mind.

So we have 2 relays. One for start one for stop. This is almost like a motor start circuit.
The stop relay is driven by a brake switch, and it would be closed when the brake is not applied. The relay is NO type, and the brake is NC, so it keeps that relay closed when power up.

For the start relay, I don't know why the start switch is closed by default, but even unplug it, it doesn't work well.
Additional circuit probably is to compare the input voltage with a set voltage (8.5v) to make sure it shut off to protect the battery.

Another one is to compare the charging plug is powered and also turn off the start relay.

#### wayneh

Joined Sep 9, 2010
17,469
Without the wiring diagram, your challenge is greater. Do you have a multimeter? If you can safely power everything with the board exposed, you can probe the board.

To prevent surprises, I'd disconnect the motor and replace it by a lightbulb. If you do something that triggers the motor, you'll get visual feedback without actually running the motor. I'd also make sure the exposed board and wiring is out of reach of any metal parts. You don't want to cause a short while you're focusing on the board and your meter readings.

I'd start by checking the inputs to the board, to verify it has power and that all control signals are actually reaching it. To check power, I'd put a 12V bulb on the boards BAT+ and BAT- terminals. This is a stronger test than merely finding 12V there with your meter. But I'd only place the load of the bulb on a circuit that you KNOW can handle the current. In other words I would not do the lightbulb test anywhere but the power lines and maybe the relay outputs if you're 100% sure you know where those are. See what voltage appears across the really coil pins when it activates. Can you hear the relays click when they should?

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#### namnguyen80

Joined May 19, 2020
12
Do you have a multimeter? If you can safely power everything with the board exposed, you can probe the board.
Can you hear the relays click when they should?
Yes, I probed the board with a multi-meter while it was powered on. What I described above was the result of that live probe.
Basically, without pressure the throttle button, power goes through the 1st relay, but it doesn't go through the second relay.
If I press the button, the 1st relay opens up, and no power going through it (to pin 13), and no power going through the 2nd relay (pin 15).

The following post describes very similar set up to mine, except the board looks different:

https://endless-sphere.com/forums/viewtopic.php?t=89541

#### wayneh

Joined Sep 9, 2010
17,469
Can you try to power a lightbulb, or your motor, directly from the board's BAT+ and BAT- terminals? Confirming there is full power there helps narrow down the problem. Likewise you can apply battery power to the first connection after the board and on the way to the motor. The idea is to eliminate any concern about the wiring harness before focusing on only the board.

#### namnguyen80

Joined May 19, 2020
12
Can you try to power a lightbulb, or your motor, directly from the board's BAT+ and BAT- terminals? Confirming there is full power there helps narrow down the problem. Likewise you can apply battery power to the first connection after the board and on the way to the motor. The idea is to eliminate any concern about the wiring harness before focusing on only the board.
Yes, the motor runs well and can carry me with the (new) battery.

#### wayneh

Joined Sep 9, 2010
17,469
Yes, the motor runs well and can carry me with the (new) battery.
Yes and that’s great but the question was whether there is adequate power at the terminals of the board. Try connecting there instead of the poles of the battery.