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Tunnel – Instantaneous online payments using Bitcoin to temporarily activate relays. Activation of automatic car wash

Scenario details:

  • We have a car wash system that works using coins. Currently, the pressure wash system is activated for 2 minutes by a relay each time a coin (1€) is inserted
  • We want to include an online payment system that works using mobile phones which activates the relay that iniciates the pressure wash system, as well as controlling the payment system
  • Bitcoin will be used as the online payment system. For every 0.002 bitcoins (approximately 1€), the pressure wash system will be activated for two minutes. If 0.004 bitcoins are received, the system will be activated for 4 minutes
  • The pressure washing system cannot be active for more than 10 consecutive minutes 
  • The user must press the button that is connected to the MTX terminal’s digital input after making the transfer in order to activate the wash system
  • The Bitcoin address associated with the MTX-Tunnel that controls the relays will be the following: 1FTvXXEJCEFuRLe9A8ZZt2865KGiGet57r

Solution: MTX-DIN-3G-Java modem + MTX-Tunnel software

EXAMPLE of settings (file config.txt) for such scenario:

GPRS_apn: movistar.es
GPRS_timeout: 0

MTX_PIN: 0000
MTX_model: MTX-DIN-3G-Java
MTX_mode: none
MTX_ping: 30
MTX_urc: on

FIREWALL_enabled: off
TELNET_enabled: on
TELNET_login: user
TELNET_password: 1234

OUTPUT_mode1: bitcoin
OUTPUT_config1: 0.002;120;1;600

WAKEUP_gpioEnabled: on
WAKEUP_gpioValue: 2

BITCOIN_enabled: on
BITCOIN_period: 15
BITCOIN_wakeup: on
BITCOIN_confirmations: 0
APN GPRS provided by the GSM operator
SIM card Username
SIM card Password
2G/3G permanent connection
If SIM card doesn’t have PIN, leave as 0000
The MTX model chosen
We do not want GPRS gateways
Ping to ensure 3G/GPRS connectivity
IP to execute the ping
URC information messages enabled
No firewall
Telnet enabled
Telnet username
Telnet password
Function mode for the relay is Bitcoin
0.002 bitcoins for 120 seconds
Digital wakeup input on to activate the system
Wakeup GPIO activated with a change in value
Bitcoin system enabled
Bitcoin address associated with MTX

System checks account every 15 secs for 3 mins
Wakeup input enabled
0 confirmations chosen as we want real time


  • The operation is simple: the client that wants to activate the relay sends the corresponding amount of Bitcoins to a Bitcoin address that is associated with the MTX terminal. After, the client presses the button that is connected to the digital wakeup input of the MTX device. MTX then changes the relay for the programmed time when it detects that the Bitcoin transaction has taken place
  • The Bitcoin address must be unique for each MTX device. Therefore, if you have 10 MTX devices, you will need to generate 10 Bitcoin addresses. These are free and you can create as many as you like
  • Use of a QR code that contains the Bitcoin address is recommended for a more user-friendly experience. All Bitcoin wallets enabled for mobile phone use allow the Bitcoin addresses to be converted from QR codes by using the camera
  • If you wish, you can convert the Bitcoins into money (€, $, etc.) using any Exchange tools (BTC-E, Coinbase, Bitstamp, etc.)
  • If you need more information about the BItcoin payment system, you can find it following these links: https://bitcoin.org/es/faq http://www.coindesk.com
  • Other examples in which temporary relay activation for payment systems can be used include: Toys activated by Coins, Timed power systems (campings), Hospital TV, Coin Washer…