5v relay in place of Motor Shield for RC Car

I am new to Arduino and the hacking of electronics together. I have been around computers since 1980. The following question is most likely extremely stupid, but I need to get started someplace learning, this appears to be the place to ask.

I am building an Arduino modified RC car. I will be adding Sonic navigation in front to start. At the time I ordered the sonic sensor, I bought a 5v relay instead of the intended motor shield.

I have bought and removed the RF receiver in the car. I have 2 wires from the front steering motor, and 2 wires from the forward/reverse motor plus positive and ground. I have an Arduino Uno and have plugged stuff into a solderless peg board for testing.

https://twitter.com/JackHBarnes/status/363151514270842882/photo/1

Can I use the relay shield as a replacement for the motor shield? What exactly is the difference between them?

http://compare.ebay.com/like/290693235593?var=lv<yp=AllFixedPriceItemTypes&var=sbar

and

http://www.sainsmart.com/sainsmart-l293d-motor-drive-shield-for-arduino-duemilanove-mega-uno-r3-avr-atmel.html?___store=en&___store=en

I am going to be using the lessons learned in this first project to build my daughters an Arduino powered Rocket Launching platform with HD camera on-board, but that is after I learn some hard lessons on the test bed above.

http://compare.ebay.com/like/160590893670?var=lv<yp=AllFixedPriceItemTypes&var=sbar

If I should go buy the motor shield, its not an issue, this is a project to learn on before I spend a couple of hundred dollars building my girls an over the top NASA like mobile hobby rocket launching platform.

In the picture above, the Uno will turn the front steering wheel barely left or right, using just the two wire leads from the motor attached to the 9,10 pins. If I plug power to the motor instead of the Arduino pins, they operate at normal speeds.

How would I get the Arduino to run these correctly, if I could just hook it up?

Will the 5v relay work as a motor shield for this project?

Thank you for any and all advice or input, its great to find a place like this.

Best,

Jack

Somebody who knows a bit more than me might be able to help better. But...

A motor shield will let you control speed, and depending on the shield direction of the motors.

A relay is pretty much just an electronic switch, it'll turn the power on or off. So only one speed.

I hope this helps.

Columnmn: Somebody who knows a bit more than me might be able to help better. But...

A motor shield will let you control speed, and depending on the shield direction of the motors.

A relay is pretty much just an electronic switch, it'll turn the power on or off. So only one speed.

I hope this helps.

Yep, you hit it on the nose. Relays will only allow you to drive 'forward' at full speed.

You can do a halfway house solution, using a transistor or transistors to provide speed control, and a DPDT relay to provide directional control. This approach used to be common in R/C ESCs, where it was easier/cheaper than providing a full H-bridge.

Thank you everyone, I have ordered a motor bridge. I will report back with an update on the vehicle once I get stuck again, or when it reaches a major milestone.