Does a MOSFET require a gate inline or pull up/down resistor when being driven from a NE555

Question

I am trying to run some indicators/flashers on my own made bicycle. I have attempted ready-made automotive flashers but have found the lights don't draw enough current for the 2-wire ones and get weird behaviour. With the 3-wire relays types I have been unable to get them to stay in sync when the hazards are activated (both left and right activated at the same time)

I have attempted to make a circuit of my own using components I have to hand.

^{simulate this circuit – Schematic created using CircuitLab}

Given the above circuit do my mosfets need any inline gate resistors or pull up/down resistors?

Is there anything else in the circuit I have overlooked or won't work as intended?

To further complicate things the switches are part of a switch cluster that shares a common positive and the lights are part of a light cluster that shares a common negative meaning I cannot alter the circuit outside of the switches and lights.

Update: Thank you for all the answers. Based on them I went with a simpler solution of using a DPDT relay driven by the 555 timer:

^{simulate this circuit}

No need to worry about driving FETs or transistors, provides a satisfying click-click and I connected the indicators to the NC-connected pins so that the indicators come on as soon as they are switched.

Answer 1

The MOSFETs need to be connected in common-source configuration. And you only need one of them. No need for a pull-down on the mosfet for basic functionality, since when the gate is not driven - when 555 is off - the lights have no power either. But to protect the MOSFET against electrostatic charge building up on the gate, a pull-down would be nice to have.

^{simulate this circuit – Schematic created using CircuitLab}

C3 charges when the bulbs are in the dark part of the cycle, and then powers U1 when M1 conducts. That way you can still use just one MOSFET, and the circuit works pretty much like an old-style blinker would - it has only two external connections :)

Answer 2

The MOSFETs don't strictly need inline gate resistors, but your original circuit doesn't drive them fully on either. This could lead to high power dissipation in the FETs and overheating.

If you exchange the position of the FETs and the lights, then the FETs will be grounded, and the VGS can be driven strongly. If your supply is '12V' and you have FETs that can take VGS = 20 V, then all is OK. However automotive '12V' can have 40 V spikes (worst case) and other transients -- you probably need some protection in your circuit for that -- for the 555 as well as the FETs. If you add an R (say 100 Ω) where the diode's cathodes join and a 15V zener to ground, you will protect both the 555 and the FETs VGS.

Note that normally flashers turn on the instant the switch is closed -- your circuit may not do that; you can fix this by connecting C1 between trigger & VCC rather than trigger and GND.